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Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 4 — Feb. 14, 2011
  • pp: 3788–3798

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40 Gb/s wavelength conversion via four-wave mixing in a quantum-dot semiconductor optical amplifier

Christian Meuer, Carsten Schmidt-Langhorst, Holger Schmeckebier, Gerrit Fiol, Dejan Arsenijević, Colja Schubert, and Dieter Bimberg  »View Author Affiliations


Optics Express, Vol. 19, Issue 4, pp. 3788-3798 (2011)
http://dx.doi.org/10.1364/OE.19.003788


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Abstract

The static and dynamic characteristics of degenerate four-wave mixing in a quantum dot semiconductor optical amplifier are investigated. A high chip conversion efficiency of 1.5 dB at 0.3 nm detuning, a low (< 5 dB) asymmetry of up and down conversion and a spectral conversion range of 15 nm with an optical signal-to-noise ratio above 20 dB is observed. The comparison of pumping near the gain peak and at the edge of the gain spectrum reveals the optical signal-to-noise ratio as the crucial parameter for error-free wavelength conversion. Small-signal bandwidths well beyond 40 GHz and 40 Gb/s error-free 5 nm wavelength down conversion with penalties below 1 dB are presented. Due to the optical signal-to-noise ratio limitation, wavelength up conversion is error-free at a pump wavelength of 1311 nm with a penalty of 2.5 dB, whereas an error floor is observed for pumping at 1291 nm. A dual pump configuration is demonstrated, to extend the wavelength conversion range enabling 15.4 nm error-free wavelength up conversion with 3.5 dB penalty caused by the additional saturation of the second pump. This is the first time that 40 Gb/s error-free wavelength conversion via four-wave mixing in quantum-dot semiconductor optical amplifiers is presented.

© 2011 OSA

1. Introduction

Recently a 100 Gb/s Ethernet standard has been defined in order to satisfy the strongly increasing demand for higher bandwidth in optical communication, required by applications such as video streaming, file sharing and video conferencing. The capacity of present networks will be extended by increasing the channel data rate, as well as by wavelength multiplexing. One possible 100 Gb/s Ethernet standard is based on four channels at a data rate of 28 Gb/s with a wavelength spacing of 5 nm for metropolitan area networks and access networks (IEEE 802.3ba). Next generation all-optical networks however, require functionalities such as wavelength conversion between adjacent channels at speeds of 40 Gb/s and beyond. Semiconductor optical amplifiers (SOAs) are promising candidates for such signal processing due to their inherent ultra-fast nonlinearities, like four-wave mixing (FWM) or cross-gain modulation [1

S. J. B. Yoo, “Wavelength conversion technologies for WDM network applications,” J. Lightwave Technol. 14(6), 955–966 (1996). [CrossRef]

].

SOAs based on quantum-dots (QDs) benefit from their unique advantages compared to conventional gain media such as quantum well or bulk materials [2

D. Bimberg, M. Kuntz, and M. Laemmlin, “Quantum dot photonic devices for lightwave communication,” Microelectron. J. 36(3-6), 175–179 (2005). [CrossRef]

, 3

D. Bimberg, M. Grundmann, and N. N. Ledentsov, Quantum Dot Heterostructures (John Wiley & Sons Ltd, Chichester, 1999).

]. Particularly, the large inhomogeneous broadening of the QD subensembles due to the distribution in size, composition and strain of the QDs results in a broad gain bandwidth [4

D. Bimberg, M. Grundmann, N. N. Ledentsov, S. S. Ruvimov, P. Werner, U. Richter, J. Heydenreich, V. M. Ustinov, P. S. Kopev, and Z. I. Alferov, “Self-organization processes in MBE-grown quantum dot structures,” Thin Solid Films 267(1-2), 32–36 (1995). [CrossRef]

]. Moreover, high saturation output power levels [5

A. V. Uskov, E. P. O'Reilly, M. Laemmlin, N. N. Ledentsov, and D. Bimberg, “On gain saturation in quantum dot semiconductor optical amplifiers,” Opt. Commun. 248(1-3), 211–219 (2005). [CrossRef]

] and ultra-fast dynamics within the QDs [6

T. Vallaitis, C. Koos, R. Bonk, W. Freude, M. Laemmlin, C. Meuer, D. Bimberg, and J. Leuthold, “Slow and fast dynamics of gain and phase in a quantum dot semiconductor optical amplifier,” Opt. Express 16(1), 170–178 (2008). [CrossRef] [PubMed]

, 7

I. O'Driscoll, T. Piwonski, C. F. Schleussner, J. Houlihan, G. Huyet, and R. J. Manning, “Electron and hole dynamics of InAs/GaAs quantum dot semiconductor optical amplifiers,” Appl. Phys. Lett. 91(26), 263506 (2007). [CrossRef]

] are advantageous for amplification as well as signal processing at 40 Gb/s [8

M. Sugawara, N. Hatori, M. Ishida, H. Ebe, Y. Arakawa, T. Akiyama, K. Otsubo, Y. Yamamoto, and Y. Nakata, “Recent progress in self-assembled quantum-dot optical devices for optical telecommunication: temperature-insensitive 10 Gb s−1 directly modulated lasers and 40 Gb s−1 signal-regenerative amplifiers,” J. Phys. D Appl. Phys. 38(13), 2126–2134 (2005). [CrossRef]

–10

R. Bonk, C. Meuer, T. Vallaitis, S. Sygletos, P. Vorreau, S. Ben-Ezra, S. Tsadka, A. Kovsh, I. Krestnikov, M. Laemmlin, D. Bimberg, W. Freude, and J. Leuthold, “Single and Multiple Channel Operation Dynamics of Linear Quantum-Dot Semiconductor Optical Amplifier,” in European Conference on Optical Communications (ECOC 2008)(Brussels, Belgium, 2008), p. Th.1.C.2.

] and beyond [11

C. Schmidt-Langhorst, C. Meuer, A. Galperin, H. Schmeckebier, R. Ludwig, D. Puris, D. Bimberg, K. Petermann, and C. Schubert, “80 Gb/s Multi-Wavelength Booster Amplification in an InGaAs/GaAs Quantum-Dot Semiconductor Optical Amplifier,” in European Conference on Optical Communication (ECOC 2010)(Torino, Italy, 2010), p. Mo.1.F.6.

,12

G. Contestabile, A. Maruta, S. Sekiguchi, K. Morito, M. Sugawara, and K. Kitayama, “Regenerative Amplification in a Quantum Dot SOA ” in Optical Fiber Communication Conference (OFC 2010)(San Diego, CA, USA, 2010), p. OMT2.

]. Wavelength conversion via cross-gain modulation was demonstrated at 40 Gb/s [13

T. Akiyama, N. Hatori, Y. Nakata, H. Ebe, and M. Sugawara, “Pattern-effect-free amplification and cross-gain modulation achieved by using ultrafast gain nonlinearity in quantum-dot semiconductor optical amplifiers,” Phys. Status Solidi, B Basic Res. 238(2), 301–304 (2003). [CrossRef]

], at 80 Gb/s for multicast conversion [14

G. Contestabile, A. Maruta, S. Sekiguchi, K. Morito, and K. Kitayama, “80 Gb/s Multicast Wavelength Conversion by XGM in a QD-SOA,” in European Conference on Optical Communication (ECOC2010)(Torino, Italy, 2010), p. Mo.2.A.3.

], and at 160 Gb/s [15

G. Contestabile, A. Maruta, S. Sekiguchi, K. Morito, M. Sugawara, and K. Kitayama, “160 Gb/s cross gain modulation in quantum dot SOA at 1550 nm,” in European Conference on Optical Communication (ECOC 2009)(Vienna, Austria, 2009), p. PDP 1.4.

].

Wavelength conversion via FWM in quantum-well SOAs has been investigated up to 100 Gb/s [16

A. E. Kelly, A. D. Ellis, D. Nesset, R. Kashyap, and D. G. Moodie, “100Gbit/s wavelength conversion using FWM in an MQW semiconductor optical amplifier,” Electron. Lett. 34(20), 1955–1956 (1998). [CrossRef]

] and for mid-span spectral inversion, i.e. for dispersion compensation, up to 80 Gb/s [17

U. Feiste, R. Ludwig, C. Schmidt, E. Dietrich, S. Diez, H. Ehrke, E. Patzak, H. G. Weber, and T. Merker, “80-Gb/s transmission over 106-km standard-fiber using optical phase conjugation in a Sagnac-interferometer,” IEEE Photon. Technol. Lett. 11(8), 1063–1065 (1999). [CrossRef]

]. Moreover, optical sampling [18

S. Diez, C. Schubert, H.-J. Ehrke, U. Feiste, R. Ludwig, E. Patzak, C. Schmidt, and H. G. Weber, “160 Gb/s all-optical demultiplexer using a hybrid gain-transparent SOA Mach-Zehnder-Interferometer,” Electron. Lett. 36(17), 1484 (2000). [CrossRef]

] and demultiplexing [19

S. L. Jansen, M. Heid, S. Spalter, E. Meissner, C. J. Weiske, A. Schopflin, D. Khoe, and H. de Waardt, “Demultiplexing 160 Gbit/s OTDM signal to 40 Gbit/s by FWM in SOA,” Electron. Lett. 38(17), 978–980 (2002). [CrossRef]

] of 160 Gb/s data signals have been shown.

The advantage of QD SOAs is the dependence of the FWM efficiency which is more symmetric for positive and negative wavelength detuning than in quantum-well or bulk SOAs [20

T. Akiyama, H. Kuwatsuka, N. Hatori, Y. Nakata, H. Ebe, and M. Sugawara, “Symmetric Highly Efficient (~0 dB) Wavelength Conversion Based on Four-Wave Mixing in Quantum Dot Optical Amplifiers,” IEEE Photon. Technol. Lett. 14(8), 1139–1141 (2002). [CrossRef]

], due to the dominance of spectral hole burning (SHB). So far wavelength conversion via FWM has been demonstrated with quantum-dash SOAs at 10 Gb/s [21

A. Capua, S. O’Duill, V. Mikhelashvili, G. Eisenstein, J. P. Reithmaier, A. Somers, and A. Forchel, “Cross talk free multi channel processing of 10 Gbit/s data via four wave mixing in a 1550 nm InAs/InP quantum dash amplifier,” Opt. Express 16(23), 19072–19077 (2008). [CrossRef]

] and via small-signal measurements up to 40 GHz with QD SOAs [22

D. Nielsen, S. L. Chuang, N. J. Kim, D. Lee, S. H. Pyun, and W. G. Jeong, “160 GHz wavelength conversion using four-wave mixing in quantum dots,” in Conference on Lasers and Electro-Optics (CLEO)(Baltimore, MD, USA, 2009).

, 23

D. Bimberg, C. Meuer, M. Laemmlin, S. Liebich, J. Kim, A. R. Kovsh, I. Krestnikov, and G. Eisenstein, “Nonlinear properties of quantum dot semiconductor optical amplifiers at 1.3 µm,” Chin. Opt. Lett. 6, 724–726 (2008). [CrossRef]

]. This is the first time that error-free 40 Gb/s NRZ large-signal wavelength conversion via FWM in QD SOAs is demonstrated. A dual pump scheme allows conversion across a larger wavelength span.

2. Epitaxy and device structure

The QD SOA material used in this work was grown by MBE and contains 10 layers of InAs QDs in an InGaAs quantum well (dots in a well) separated by 33 nm thick GaAs spacer layers. The QDs are 5 nm in height and 15 to 20 nm in lateral extension with a surface density of 3 - 5∙1010/cm2 [24

A. R. Kovsh, N. A. Maleev, A. E. Zhukov, S. S. Mikhrin, A. P. Vasil'ev, E. A. Semenova, Y. M. Shernyakov, M. V. Maximov, D. A. Livshits, V. M. Ustinov, N. N. Ledentsov, D. Bimberg, and Z. I. Alferov, “InAs/InGaAs/GaAs quantum dot lasers of 1.3 µm range with enhanced optical gain,” J. Cryst. Growth 251(1-4), 729–736 (2003). [CrossRef]

]. Gain is predominantly provided for the TE polarization (TE/TM ratio ~10 dB). Vertical wave guiding is achieved by sandwiching the active region between 1.5 µm thick AlGaAs cladding layers. It should be noted, that the spacer layers within the active region are undoped, since p-doping has been shown to decrease the FWM efficiency [25

C. Meuer, H. Schmeckebier, G. Fiol, D. Arsenijevic, J. Kim, G. Eisenstein, and D. Bimberg, “Cross-Gain Modulation and Four-Wave Mixing for Wavelength Conversion in undoped and p-doped 1.3 µm Quantum Dot Semiconductor Optical Amplifiers,” IEEE Photon. 2(2), 141–151 (2010). [CrossRef]

].

The QD SOAs presented here are 3 mm long and 4 µm broad shallow etched ridge waveguide structures. In addition to an anti-reflective coating of the facets the waveguides are tilted at 8° with respect to the facets resulting in a gain ripple below 0.3 dB. The maximum linear fiber-to-fiber gain occurs at 250 mA near 1295 nm and is found to be 16 dB (25 dB chip gain). At this current, the 3 dB saturation output power in the fiber was 13 dBm. At larger currents the peak linear gain decreases and experiences a red shift due to heating of the device, whereas the saturation output power keeps increasing. Amplified spontaneous emission (ASE) spectra are presented in Fig. 1 showing their evolution in dependence on the current. The QD SOA ASE spectra consist of the ground state (GS) emission, which is in resonance with the light to be amplified, and the excited states (ES) emission. The ESs and the surrounding quantum well refill the GS and act as a carrier reservoir. The vertical blue lines indicate the spectral positions of the two pump signals at 1291 nm and 1311 nm used in the experiments below. The former is near the gain peak, whereas the latter one is on the long wavelength edge of the gain spectrum.

Fig. 1 ASE spectra at various injection currents. The vertical blue lines denote the wavelengths of the pump signals at 1291 nm and 1311 nm.

3. Experiments and results

3.1 Static four-wave-mixing efficiency and small-signal measurements

To compare the behavior of FWM at different pump wavelengths, DFB lasers emitting at 1291 nm or 1311 nm are injected as pump signals. The probe signal is generated by a wavelength tunable external cavity laser (ECL). The output spectra are recorded with an optical spectrum analyzer and evaluated in terms of FWM efficiency and optical signal-to-noise ratio (OSNR) within 0.1 nm. The FWM efficiency is defined as ratio of the output power of the FWM conjugate to the input probe power, while the detuning is defined as the difference between the wavelengths of the probe signal and the pump signal (Δλ=λprobe-λpump).

The static FWM efficiency as a function of the pump power at 1291 nm is shown in Fig. 2(a) for various currents at a detuning of 1 nm. A saturation behavior of the FWM efficiency is observed at large input power levels. At a current of 200 mA a maximum conversion efficiency of −16.8 dB is reached at pump power levels above 6 dBm. The saturated conversion efficiency increases to −11.4 dB and −9.4 dB at 350 mA and 500 mA, respectively, whereas at 650 mA a pump power of 11 dBm is not sufficient to achieve full saturation of the FWM efficiency. A FWM efficiency of −8.8 dB is measured at 650 mA.

Fig. 2 (a) Dependence of the FWM efficiency on the pump power at 1 nm detuning for different operating currents of the QD SOA. (b, solid symbols) FWM efficiency as a function of the pump power for probe power levels of −8, −3 and 2 dBm and (open symbols) corresponding optical signal-to-noise ratio.

Increasing the current results in an increasing saturation output power and thus leads to larger FWM efficiencies at large pump power levels, although the maximum small-signal GS gain is already found for 250 mA. The lower FWM efficiency at 650 mA and small pump power levels can be explained by heating of the device, which reduces the small-signal gain and limits the maximum current which can be applied.

The probe power does not significantly influence the FWM efficiency (Fig. 2(b)), however the OSNR improves linearly with increasing probe power.

The FWM efficiency as a function of the detuning is shown in Fig. 3 . Large currents significantly increase the detuning range in which the FWM exceeds the ASE noise floor of the QD SOA due to the dominance of SHB. If the QD SOA is pumped at 1291 nm (Fig. 3(a)), a FWM efficiency of −7.5 dB is observed at a positive detuning (down conversion) of 0.3 nm and 650mA. Including the coupling losses of 4.5 dB per facet yields a chip-FWM efficiency of 1.5dB.

Fig. 3 Dependence of the FWM efficiency on the pump-probe detuning for different operating currents at a pump wavelength of (a) 1291 nm and (b) 1311 nm.

The detuning range, in which the FWM signal exceeds the noise floor, is symmetric for up and down conversion and is as large as 55 nm at 650 mA. These results agree with results presented in [20

T. Akiyama, H. Kuwatsuka, N. Hatori, Y. Nakata, H. Ebe, and M. Sugawara, “Symmetric Highly Efficient (~0 dB) Wavelength Conversion Based on Four-Wave Mixing in Quantum Dot Optical Amplifiers,” IEEE Photon. Technol. Lett. 14(8), 1139–1141 (2002). [CrossRef]

]. If the detuning is less than 15 nm at large currents, the FWM efficiency is 4 dB to 5 dB smaller for negative detuning (up conversion to longer wavelengths) owing to the non-zero alpha factor. Carrier heating and carrier density pulsation within the carrier reservoir cause the asymmetry [26

A. Bilenca, R. Alizon, V. Mikhelashhvili, D. Dahan, G. Eisenstein, R. Schwertberger, D. Gold, J. P. Reithmaier, and A. Forchel, “Broad-band wavelength conversion based on cross-gain modulation and four-wave mixing in InAs-InP quantum-dash semiconductor optical amplifiers operating at 1550 nm,” IEEE Photon. Technol. Lett. 15(4), 563–565 (2003). [CrossRef]

, 27

D. Nielsen, S. L. Chuang, N. J. Kim, D. Lee, S. H. Pyun, W. G. Jeong, C. Y. Chen, and T. S. Lay, “High-speed wavelength conversion in quantum dot and quantum well semiconductor optical amplifiers,” Appl. Phys. Lett. 92(21), 211101 (2008). [CrossRef]

], since these effects interfere constructively at positive and destructively at negative detuning, well known from conventional SOAs [28

K. Kikuchi, M. Kakui, C. E. Zah, and T. P. Lee, “Observation of Highly Nondegenerate 4-Wave-Mixing in 1.5 µm Traveling-Wave Semiconductor Optical Amplifiers and Estimation of Nonlinear Gain Coefficient,” IEEE J. Quantum Electron. 28(1), 151–156 (1992). [CrossRef]

]. For pumping at 1311 nm (Fig. 3(b)) a slightly smaller FWM efficiency of −11.2 dB is found at 0.65 nm detuning (−10.2 dB at 1291 nm and 0.65 nm detuning). The efficiency at negative detuning is smaller, similar to pumping at 1291 nm.

An OSNR above 20 dB is achieved at 1291 nm pump wavelength within a 14 nm span (−5 nm to 9 nm detuning) (Fig. 4(a) ). At 1311 nm, however, due to the fact that the gain increases strongly towards shorter wavelengths, the OSNR is enhanced at negative detuning due to the lower ASE level at the wavelength of the FWM conjugate. In consequence the OSNR is larger than 20 dB across a 14.5 nm span (−8 nm to 6.5 nm detuning) at 650 mA (Fig. 4(b)) and more symmetric than for pumping at 1291 nm. Since the large signal measurements shown below are conducted at 2.5 nm detuning, the corresponding values of the FWM efficiency and the OSNR are listed in Table 1 .

Fig. 4 Dependence of OSNR on the pump-probe detuning for different operating currents at a pump wavelength of (a) 1291 nm and (b) 1311 nm.
Table 1  Values of the FWM efficiency and the OSNR at 2.5 nm and −2.5 nm detuning for the pump wavelengths of 1291 nm and 1311 nm and a current of 650 mA.
Pump wavelength
1291 nm
1311 nm
Conversion typeupdownupdown
Detuning−2.5 nm2.5 nm−2.5 nm2.5 nm
FWM efficiency−21.0 dB−16.0 dB−23.4 dB−19.2 dB
OSNR22.9 dB28.9 dB24.0 dB27.0 dB

The efficiency at 1291 nm pump wavelength is 2-3 dB larger than at 1311 nm, due to the larger gain near the gain peak. Similarly, the OSNR is 1.9 dB larger for down conversion at 1291 nm than at 1311 nm. In contrast to that the OSNR is 1.1 dB larger for up conversion at 1311 nm due to the lower ASE level at the wavelength of the FWM product.

Small-signal FWM measurements at 1291 nm (Fig. 5 ) show FWM bandwidths well beyond 40 GHz (consistent with results presented in [22

D. Nielsen, S. L. Chuang, N. J. Kim, D. Lee, S. H. Pyun, and W. G. Jeong, “160 GHz wavelength conversion using four-wave mixing in quantum dots,” in Conference on Lasers and Electro-Optics (CLEO)(Baltimore, MD, USA, 2009).

]) within a 16 nm detuning range, demonstrating the fast dynamics of FWM in QD SOAs independent of the current (Fig. 5(a)) and the detuning (Fig. 5(b)) up to the experimental limit of 40 GHz.

Fig. 5 (a) FWM efficiency dependent on the modulation frequency at different currents and (b) normalized FWM efficiency as a function of the detuning at various frequencies deduced from small-signal measurements. The FWM traces dependent on the modulation frequency are normalized to their respective maximum to get of the influence of the gain spectrum. Only values at distinct frequencies are shown as a function of the wavelength in (b).

3.2 Large-signal wavelength conversion via four-wave mixing

Large-signal wavelength conversion (WC) experiments were conducted at a data rate of 40 Gb/s. The probe signal from the ECL is modulated with a pseudo-random binary sequence (PRBS) having a length of 231-1 (Fig. 6 ). The resulting non-return-to-zero (NRZ) signal is injected to the QD SOA together with the cw pump signal either at 1291 nm or 1311 nm. After the QD SOA the FWM conjugate signal is filtered using fiber-Bragg gratings. Additional gratings serve as notch filters to further suppress the pump and data signals. The wavelength converted signal is detected with a preamplified receiver consisting of two Praseodymium doped fiber amplifiers (PDFAs) in combination with a 50 GHz photo diode optimized for the O-band. Bit-error ratios (BER) as well as eye diagrams of the received signal can be measured. The probe power is set to 6 dBm instead of 2 dBm in the static measurements to enhance the OSNR of the conjugate signal.

Fig. 6 Setup for wavelength conversion via FWM and successive bit-error-ratio measurements of a 40 Gb/s PRBS 231-1 NRZ data signal either around 1291 nm or 1311 nm. ECL: external cavity laser, DFB: distributed feedback laser, MZM: Mach-Zehnder modulator, PDFA: Praseodymium doped fiber amplifier, FBG: fiber-Bragg grating, WDM Mux: wavelength division multiplexer, QW SOA: quantum-well SOA, ISO: Isolator, VOA: variable optical attenuator, PD: photo diode, PWM: optical power meter.

Figure 7 shows eye diagrams of an unconverted signal at 1288 nm (Fig. 7(b)) and the down converted signal (1293.5 nm to 1288.7 nm, Fig. 7(b)) at a BER of 10−9. A low signal distortion is observed after conversion indicating strongly suppressed patterning effects.

Fig. 7 Eye diagrams of (a) a back-to-back signal at 1288 nm and (b) the down converted signal (1293 nm to 1288 nm) at a BER of 10-9.

BER measurements for 5 nm wavelength conversion (i.e. 2.5 nm detuning) are shown in Fig. 8 and 9 for down and up conversion, respectively. Error-free 40 Gb/s NRZ wavelength conversion via FWM in QD SOAs is presented for the first time. Wavelength down conversion by −4.8 nm (positive detuning) around 1291 nm pump wavelength (Fig. 8(a)) is found to be error-free with a negligible penalty of 0.2 dB at a BER of 10−9 in comparison to the back-to-back measurement. A penalty of 0.9 dB is found at a BER of 10−9 (Fig. 8(b)) for down conversion at 1311 nm due to the slightly lower FWM efficiency and OSNR.

Fig. 8 BER versus received power for 5 nm wavelength down conversion at a pump wavelength of (a) 1291 nm and (b) 1311 nm.
Fig. 9 BER as a function of the received power for 5 nm wavelength up conversion at (a) 1291 nm and (b) 1311 nm. The dashed red line is an extrapolation of the BER curve for estimation of the penalty at a BER of 10−9.

The low FWM efficiency and small OSNR (see Table 1) cause an error floor at a BER of 10−9 for wavelength up conversion at 1291 nm (Fig. 9(a)), whereas the OSNR of the signal up converted around 1311nm (Fig. 9(b)) is sufficient to enable error-free conversion with an estimated penalty of 2.5 dB. This penalty has been derived via extrapolation, since the maximum received power was limited to −24 dBm.

Thus, error-free wavelength conversion via FWM in QD SOAs is feasible, if the OSNR of the converted signal is sufficient. Present devices are not yet optimized for high nonlinearity. An adaption of the waveguide design or a change of the epitaxial structure allow for an improvement of the OSNR performance of the QD SOAs and will be subject to further studies. There is a potential to surpass the performance of the best quantum-well devices reported in [29

A. E. Kelly, D. D. Marcenac, and D. Nesset, “40Gbit/s wavelength conversion over 24.6nm using FWM in a semiconductor optical amplifier with an optimised MQW active region,” Electron. Lett. 33(25), 2123–2124 (1997). [CrossRef]

] in particular for wavelength up conversion due to the symmetric four-wave mixing efficiency for up and down conversion.

3.3 Wavelength conversion via FWM using multiple pump signals

The range for wavelength conversion with a single pump signal is limited by the decaying FWM efficiency and the accompanying decrease of the OSNR at larger pump-probe detuning as shown above. First investigations on multi-channel wavelength conversion via FWM in quantum-dash SOAs have demonstrated a broadband (~30 nm) interaction between different dash subensembles [21

A. Capua, S. O’Duill, V. Mikhelashvili, G. Eisenstein, J. P. Reithmaier, A. Somers, and A. Forchel, “Cross talk free multi channel processing of 10 Gbit/s data via four wave mixing in a 1550 nm InAs/InP quantum dash amplifier,” Opt. Express 16(23), 19072–19077 (2008). [CrossRef]

] mediated through the reservoir and leading to cross talk if two wavelength channels are converted at the same pump-probe detuning. On the other hand, it is well known from conventional SOAs, that the injection of a second pump signal enables an extension of the conversion range taking advantage of this broadband interaction [30

G. Grosskopf, R. Ludwig, and H. G. Weber, “140 Mbit/s DPSK Transmission Using an All-Optical Frequency-Converter with a 4000 GHz Conversion Range,” Electron. Lett. 24(17), 1106–1107 (1988). [CrossRef]

–34

I. Tomkos, I. Zacharopoulos, D. Syvridis, T. Sphicopoulos, and E. Roditi, “Improved performance of a wavelength converter based on dual pump four-wave mixing in a bulk semiconductor optical amplifier,” Appl. Phys. Lett. 72(20), 2499–2501 (1998). [CrossRef]

]. In this experiment, both pump signals in Fig. 10 are parallel polarized and adjusted for maximum TE gain. The output spectrum for dual pump operation of the QD SOA is shown in Fig. 10(a). The data signal at 1293.5 nm is down converted to 1288.7 nm via the first pump at 1291 nm. Additional frequency components appear, detuned by 2.5 nm around the second pump at 1311 nm. Further groups of FWM products are generated between 1271 nm and 1276 nm as well as between 1331 nm and 1334 nm by FWM of the pump signals as well as the data signal with the second pump. The initial data signal at 1293.5 nm is converted to three other wavelengths (1288.7nm, 1308.9 nm and 1313.7nm) with FWM power levels of −24 dBm, −24.6 dBm and −29.3 dBm, respectively. Additional gain compression by the second pump signal reduces the FWM efficiency at 1288.7 nm by 5 dB (Fig. 10(b)). The conversion from 1293.5 nm to 1308.9 nm results in an only 0.6 dB lower FWM power than for the 5 nm down conversion to 1288.7 nm.

Fig. 10 (a) Output spectrum of the QD SOA after FWM generation using two pump signals (pump 1 at 1291 nm and pump 2 at 1311 nm) both with an input power of 12 dBm. The data signal (1293.5 nm) is converted to conjugate 1 (1288.7), conjugate 2 (1308.9 nm) and conjugate 3 (1313.7 nm). (b) Zoom of the FWM conjugate 1 demonstrating the 5 dB reduction of the FWM power if the second pump is additionally injected to the QD SOA.

BER measurements of the 5 nm down converted signal at 1288.7 nm show an increased penalty of 3.5 dB due to the second pump (Fig. 11(a) ). An equal penalty of 3.4 dB is observed for up conversion by 15 nm to 1308.9 nm (Fig. 11(b)). Thus the possibility to extend the conversion range with a second pump beyond the homogeneous linewidth in QD SOAs is demonstrated. Conversion seems to be feasible across the whole gain spectrum as long as sufficient gain is available. In the dual pump case up conversion is possible with identical properties to down conversion in contrast to the single pump case.

Fig. 11 (a) BER as a function of the received power for wavelength down conversion with a single pump at 1291 nm (red circles, same as in Fig. 8(a)) and for the dual pump configuration (green triangles). (b) BER vs. received power for dual pump wavelength up conversion from 1293.5 nm to 1308.9 nm (green triangles).

The third FWM conjugate at 1313.7 nm shows comparable BER characteristics, but the lower power prevented measurements below 10−6 BER.

The effect of efficient broadband interaction mediated by FWM might be explained by modulation of the carrier distribution in the reservoir as discussed in the following. The QDs themselves are spatially isolated, i.e. tunneling of carriers from one QD to another is prohibited. In consequence, the gain change caused by spectral hole burning cannot directly affect the gain at a wavelength beyond the homogeneous broadening. However, the carrier reservoir in the higher energy states (first of all the surrounding QW) is common to all the QDs. Hence, the reservoir should mediate the interaction between different subensembles.

The beating of the first pump signal and the data signal at the frequency Δω modulates the gain of a QD subensemble at the beat frequency. The gain recovers by Auger scattering, i.e. carrier capture from the reservoir into the QDs. Due to the energy difference between the QD states and the reservoir states, the Auger processes induce strong carrier heating. The carrier heating in the reservoir is also modulated at Δω and determines a temporal dependence of the carrier capture rate into and thus the gain of all the QDs. Therefore, a QD subensemble could indirectly influence the gain of all the other QDs and in particular the gain of the second pump signal via carrier heating. The modulation of the gain experienced by the second pump signal leads to the generation of the conjugate components 2 and 3 in Fig. 10(a).

Carrier density pulsation is limited to bandwidths of 5 - 10 GHz and therefore unlikely to be the dominating effect for this interaction.

Typical time constants for the relaxation of carrier heating range from 500 fs to 650 fs for conventional amplifiers [35

S. Diez, C. Schmidt, R. Ludwig, H. G. Weber, K. Obermann, S. Kindt, I. Koltchanov, and K. Petermann, “Four-wave mixing in semiconductor optical amplifiers for frequency conversion and fast optical switching,” IEEE J. Sel. Top. Quantum Electron. 3(5), 1131–1145 (1997). [CrossRef]

]. Due to the large energy difference of the QD states and the reservoir, the relaxation may be slower (1-2 ps) in QD SOAs. Although the dynamics of carrier heating is approximately by a factor of 5-10 slower than the recovery of SHB [36

P. Borri, W. Langbein, J. M. Hvam, F. Heinrichsdorff, H.-M. Mao, and D. Bimberg, “Spectral Hole-Burning and Carrier-Heating Dynamics in InGaAs Quantum-Dot Amplifiers,” IEEE J. Sel. Top. Quantum Electron. 6(3), 544–551 (2000). [CrossRef]

], which is the fastest process in QD SOAs, it should enable high-speed dynamics sufficient for signal processing at 100 Gb/s.

4. Conclusion

40 Gb/s wavelength conversion of NRZ-signals across +/−5 nm via FWM in 1.3 µm QD SOAs is demonstrated for the first time. The penalties are 0.2 dB and 0.9 dB for wavelength down conversion at 1291 nm and 1311 nm, respectively, whereas up conversion shows an error floor at a BER of 10−9 at 1291 nm due to the OSNR limitation. The better OSNR of the up- converted signal at 1311 nm enables error-free up conversion with a penalty of 2.5 dB. In a dual pump configuration the detuning range is significantly extended and wavelength conversion experiments demonstrate wavelength up conversion by 15.4 nm having the same BER characteristics as 5 nm wavelength down conversion in the dual pump case. The penalty of 3.5 dB is mainly caused by the additional saturation induced by the second pump. The underlying physical process responsible for this spectrally broadband interaction is most probably carrier heating within the reservoir. This reservoir is common to all QD subensembles enabling high-speed interaction beyond the range of the homogeneous broadening.

Acknowledgment

This work was supported by the research center SFB 787 of the German Research Foundation (DFG). The authors would like to thank K. Janiak and R. Molt from the Fraunhofer Heinrich Hertz Institute, Berlin, for assistance with the AR-coating of the QD SOAs.

References and links

1.

S. J. B. Yoo, “Wavelength conversion technologies for WDM network applications,” J. Lightwave Technol. 14(6), 955–966 (1996). [CrossRef]

2.

D. Bimberg, M. Kuntz, and M. Laemmlin, “Quantum dot photonic devices for lightwave communication,” Microelectron. J. 36(3-6), 175–179 (2005). [CrossRef]

3.

D. Bimberg, M. Grundmann, and N. N. Ledentsov, Quantum Dot Heterostructures (John Wiley & Sons Ltd, Chichester, 1999).

4.

D. Bimberg, M. Grundmann, N. N. Ledentsov, S. S. Ruvimov, P. Werner, U. Richter, J. Heydenreich, V. M. Ustinov, P. S. Kopev, and Z. I. Alferov, “Self-organization processes in MBE-grown quantum dot structures,” Thin Solid Films 267(1-2), 32–36 (1995). [CrossRef]

5.

A. V. Uskov, E. P. O'Reilly, M. Laemmlin, N. N. Ledentsov, and D. Bimberg, “On gain saturation in quantum dot semiconductor optical amplifiers,” Opt. Commun. 248(1-3), 211–219 (2005). [CrossRef]

6.

T. Vallaitis, C. Koos, R. Bonk, W. Freude, M. Laemmlin, C. Meuer, D. Bimberg, and J. Leuthold, “Slow and fast dynamics of gain and phase in a quantum dot semiconductor optical amplifier,” Opt. Express 16(1), 170–178 (2008). [CrossRef] [PubMed]

7.

I. O'Driscoll, T. Piwonski, C. F. Schleussner, J. Houlihan, G. Huyet, and R. J. Manning, “Electron and hole dynamics of InAs/GaAs quantum dot semiconductor optical amplifiers,” Appl. Phys. Lett. 91(26), 263506 (2007). [CrossRef]

8.

M. Sugawara, N. Hatori, M. Ishida, H. Ebe, Y. Arakawa, T. Akiyama, K. Otsubo, Y. Yamamoto, and Y. Nakata, “Recent progress in self-assembled quantum-dot optical devices for optical telecommunication: temperature-insensitive 10 Gb s−1 directly modulated lasers and 40 Gb s−1 signal-regenerative amplifiers,” J. Phys. D Appl. Phys. 38(13), 2126–2134 (2005). [CrossRef]

9.

G. Contestabile, A. Maruta, S. Sekiguchi, K. Morito, M. Sugawara, and K. Kitayama, “Regenerative Amplification by Using Self-Phase Modulation in a Quantum-Dot SOA,” IEEE Photon. Technol. Lett. 22(7), 492–494 (2010). [CrossRef]

10.

R. Bonk, C. Meuer, T. Vallaitis, S. Sygletos, P. Vorreau, S. Ben-Ezra, S. Tsadka, A. Kovsh, I. Krestnikov, M. Laemmlin, D. Bimberg, W. Freude, and J. Leuthold, “Single and Multiple Channel Operation Dynamics of Linear Quantum-Dot Semiconductor Optical Amplifier,” in European Conference on Optical Communications (ECOC 2008)(Brussels, Belgium, 2008), p. Th.1.C.2.

11.

C. Schmidt-Langhorst, C. Meuer, A. Galperin, H. Schmeckebier, R. Ludwig, D. Puris, D. Bimberg, K. Petermann, and C. Schubert, “80 Gb/s Multi-Wavelength Booster Amplification in an InGaAs/GaAs Quantum-Dot Semiconductor Optical Amplifier,” in European Conference on Optical Communication (ECOC 2010)(Torino, Italy, 2010), p. Mo.1.F.6.

12.

G. Contestabile, A. Maruta, S. Sekiguchi, K. Morito, M. Sugawara, and K. Kitayama, “Regenerative Amplification in a Quantum Dot SOA ” in Optical Fiber Communication Conference (OFC 2010)(San Diego, CA, USA, 2010), p. OMT2.

13.

T. Akiyama, N. Hatori, Y. Nakata, H. Ebe, and M. Sugawara, “Pattern-effect-free amplification and cross-gain modulation achieved by using ultrafast gain nonlinearity in quantum-dot semiconductor optical amplifiers,” Phys. Status Solidi, B Basic Res. 238(2), 301–304 (2003). [CrossRef]

14.

G. Contestabile, A. Maruta, S. Sekiguchi, K. Morito, and K. Kitayama, “80 Gb/s Multicast Wavelength Conversion by XGM in a QD-SOA,” in European Conference on Optical Communication (ECOC2010)(Torino, Italy, 2010), p. Mo.2.A.3.

15.

G. Contestabile, A. Maruta, S. Sekiguchi, K. Morito, M. Sugawara, and K. Kitayama, “160 Gb/s cross gain modulation in quantum dot SOA at 1550 nm,” in European Conference on Optical Communication (ECOC 2009)(Vienna, Austria, 2009), p. PDP 1.4.

16.

A. E. Kelly, A. D. Ellis, D. Nesset, R. Kashyap, and D. G. Moodie, “100Gbit/s wavelength conversion using FWM in an MQW semiconductor optical amplifier,” Electron. Lett. 34(20), 1955–1956 (1998). [CrossRef]

17.

U. Feiste, R. Ludwig, C. Schmidt, E. Dietrich, S. Diez, H. Ehrke, E. Patzak, H. G. Weber, and T. Merker, “80-Gb/s transmission over 106-km standard-fiber using optical phase conjugation in a Sagnac-interferometer,” IEEE Photon. Technol. Lett. 11(8), 1063–1065 (1999). [CrossRef]

18.

S. Diez, C. Schubert, H.-J. Ehrke, U. Feiste, R. Ludwig, E. Patzak, C. Schmidt, and H. G. Weber, “160 Gb/s all-optical demultiplexer using a hybrid gain-transparent SOA Mach-Zehnder-Interferometer,” Electron. Lett. 36(17), 1484 (2000). [CrossRef]

19.

S. L. Jansen, M. Heid, S. Spalter, E. Meissner, C. J. Weiske, A. Schopflin, D. Khoe, and H. de Waardt, “Demultiplexing 160 Gbit/s OTDM signal to 40 Gbit/s by FWM in SOA,” Electron. Lett. 38(17), 978–980 (2002). [CrossRef]

20.

T. Akiyama, H. Kuwatsuka, N. Hatori, Y. Nakata, H. Ebe, and M. Sugawara, “Symmetric Highly Efficient (~0 dB) Wavelength Conversion Based on Four-Wave Mixing in Quantum Dot Optical Amplifiers,” IEEE Photon. Technol. Lett. 14(8), 1139–1141 (2002). [CrossRef]

21.

A. Capua, S. O’Duill, V. Mikhelashvili, G. Eisenstein, J. P. Reithmaier, A. Somers, and A. Forchel, “Cross talk free multi channel processing of 10 Gbit/s data via four wave mixing in a 1550 nm InAs/InP quantum dash amplifier,” Opt. Express 16(23), 19072–19077 (2008). [CrossRef]

22.

D. Nielsen, S. L. Chuang, N. J. Kim, D. Lee, S. H. Pyun, and W. G. Jeong, “160 GHz wavelength conversion using four-wave mixing in quantum dots,” in Conference on Lasers and Electro-Optics (CLEO)(Baltimore, MD, USA, 2009).

23.

D. Bimberg, C. Meuer, M. Laemmlin, S. Liebich, J. Kim, A. R. Kovsh, I. Krestnikov, and G. Eisenstein, “Nonlinear properties of quantum dot semiconductor optical amplifiers at 1.3 µm,” Chin. Opt. Lett. 6, 724–726 (2008). [CrossRef]

24.

A. R. Kovsh, N. A. Maleev, A. E. Zhukov, S. S. Mikhrin, A. P. Vasil'ev, E. A. Semenova, Y. M. Shernyakov, M. V. Maximov, D. A. Livshits, V. M. Ustinov, N. N. Ledentsov, D. Bimberg, and Z. I. Alferov, “InAs/InGaAs/GaAs quantum dot lasers of 1.3 µm range with enhanced optical gain,” J. Cryst. Growth 251(1-4), 729–736 (2003). [CrossRef]

25.

C. Meuer, H. Schmeckebier, G. Fiol, D. Arsenijevic, J. Kim, G. Eisenstein, and D. Bimberg, “Cross-Gain Modulation and Four-Wave Mixing for Wavelength Conversion in undoped and p-doped 1.3 µm Quantum Dot Semiconductor Optical Amplifiers,” IEEE Photon. 2(2), 141–151 (2010). [CrossRef]

26.

A. Bilenca, R. Alizon, V. Mikhelashhvili, D. Dahan, G. Eisenstein, R. Schwertberger, D. Gold, J. P. Reithmaier, and A. Forchel, “Broad-band wavelength conversion based on cross-gain modulation and four-wave mixing in InAs-InP quantum-dash semiconductor optical amplifiers operating at 1550 nm,” IEEE Photon. Technol. Lett. 15(4), 563–565 (2003). [CrossRef]

27.

D. Nielsen, S. L. Chuang, N. J. Kim, D. Lee, S. H. Pyun, W. G. Jeong, C. Y. Chen, and T. S. Lay, “High-speed wavelength conversion in quantum dot and quantum well semiconductor optical amplifiers,” Appl. Phys. Lett. 92(21), 211101 (2008). [CrossRef]

28.

K. Kikuchi, M. Kakui, C. E. Zah, and T. P. Lee, “Observation of Highly Nondegenerate 4-Wave-Mixing in 1.5 µm Traveling-Wave Semiconductor Optical Amplifiers and Estimation of Nonlinear Gain Coefficient,” IEEE J. Quantum Electron. 28(1), 151–156 (1992). [CrossRef]

29.

A. E. Kelly, D. D. Marcenac, and D. Nesset, “40Gbit/s wavelength conversion over 24.6nm using FWM in a semiconductor optical amplifier with an optimised MQW active region,” Electron. Lett. 33(25), 2123–2124 (1997). [CrossRef]

30.

G. Grosskopf, R. Ludwig, and H. G. Weber, “140 Mbit/s DPSK Transmission Using an All-Optical Frequency-Converter with a 4000 GHz Conversion Range,” Electron. Lett. 24(17), 1106–1107 (1988). [CrossRef]

31.

N. Schunk, G. Groβkopt, R. Ludwig, R. Schnabel, and H. G. Weber, “Frequency-Conversion by Nearly-Degenerate 4-Wave-Mixing in Traveling-Wave Semiconductor-Laser Amplifiers,” IEE Proc. Optoelectron. 137, 209–214 (1990). [CrossRef]

32.

G. Contestabile, F. Martelli, A. Mecozzi, L. Graziani, A. D'Ottavi, P. Spano, G. Guekos, R. Dall'Ara, and J. Eckner, “Efficiency flattening and equalization of frequency up- and down-conversion using four-wave mixing in semiconductor optical amplifiers,” IEEE Photon. Technol. Lett. 10(10), 1398–1400 (1998). [CrossRef]

33.

T. J. Morgan, J. P. R. Lacey, and R. S. Tucker, “Widely tunable four-wave mixing in semiconductor optical amplifiers with constant conversion efficiency,” IEEE Photon. Technol. Lett. 10(10), 1401–1403 (1998). [CrossRef]

34.

I. Tomkos, I. Zacharopoulos, D. Syvridis, T. Sphicopoulos, and E. Roditi, “Improved performance of a wavelength converter based on dual pump four-wave mixing in a bulk semiconductor optical amplifier,” Appl. Phys. Lett. 72(20), 2499–2501 (1998). [CrossRef]

35.

S. Diez, C. Schmidt, R. Ludwig, H. G. Weber, K. Obermann, S. Kindt, I. Koltchanov, and K. Petermann, “Four-wave mixing in semiconductor optical amplifiers for frequency conversion and fast optical switching,” IEEE J. Sel. Top. Quantum Electron. 3(5), 1131–1145 (1997). [CrossRef]

36.

P. Borri, W. Langbein, J. M. Hvam, F. Heinrichsdorff, H.-M. Mao, and D. Bimberg, “Spectral Hole-Burning and Carrier-Heating Dynamics in InGaAs Quantum-Dot Amplifiers,” IEEE J. Sel. Top. Quantum Electron. 6(3), 544–551 (2000). [CrossRef]

OCIS Codes
(190.4380) Nonlinear optics : Nonlinear optics, four-wave mixing
(250.5980) Optoelectronics : Semiconductor optical amplifiers

ToC Category:
Nonlinear Optics

History
Original Manuscript: December 20, 2010
Revised Manuscript: February 2, 2011
Manuscript Accepted: February 2, 2011
Published: February 11, 2011

Citation
Christian Meuer, Carsten Schmidt-Langhorst, Holger Schmeckebier, Gerrit Fiol, Dejan Arsenijević, Colja Schubert, and Dieter Bimberg, "40 Gb/s wavelength conversion via four-wave mixing in a quantum-dot semiconductor optical amplifier," Opt. Express 19, 3788-3798 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-4-3788


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References

  1. S. J. B. Yoo, “Wavelength conversion technologies for WDM network applications,” J. Lightwave Technol. 14(6), 955–966 (1996). [CrossRef]
  2. D. Bimberg, M. Kuntz, and M. Laemmlin, “Quantum dot photonic devices for lightwave communication,” Microelectron. J. 36(3-6), 175–179 (2005). [CrossRef]
  3. D. Bimberg, M. Grundmann, and N. N. Ledentsov, Quantum Dot Heterostructures (John Wiley & Sons Ltd, Chichester, 1999).
  4. D. Bimberg, M. Grundmann, N. N. Ledentsov, S. S. Ruvimov, P. Werner, U. Richter, J. Heydenreich, V. M. Ustinov, P. S. Kopev, and Z. I. Alferov, “Self-organization processes in MBE-grown quantum dot structures,” Thin Solid Films 267(1-2), 32–36 (1995). [CrossRef]
  5. A. V. Uskov, E. P. O'Reilly, M. Laemmlin, N. N. Ledentsov, and D. Bimberg, “On gain saturation in quantum dot semiconductor optical amplifiers,” Opt. Commun. 248(1-3), 211–219 (2005). [CrossRef]
  6. T. Vallaitis, C. Koos, R. Bonk, W. Freude, M. Laemmlin, C. Meuer, D. Bimberg, and J. Leuthold, “Slow and fast dynamics of gain and phase in a quantum dot semiconductor optical amplifier,” Opt. Express 16(1), 170–178 (2008). [CrossRef] [PubMed]
  7. I. O'Driscoll, T. Piwonski, C. F. Schleussner, J. Houlihan, G. Huyet, and R. J. Manning, “Electron and hole dynamics of InAs/GaAs quantum dot semiconductor optical amplifiers,” Appl. Phys. Lett. 91(26), 263506 (2007). [CrossRef]
  8. M. Sugawara, N. Hatori, M. Ishida, H. Ebe, Y. Arakawa, T. Akiyama, K. Otsubo, Y. Yamamoto, and Y. Nakata, “Recent progress in self-assembled quantum-dot optical devices for optical telecommunication: temperature-insensitive 10 Gb s−1 directly modulated lasers and 40 Gb s−1 signal-regenerative amplifiers,” J. Phys. D Appl. Phys. 38(13), 2126–2134 (2005). [CrossRef]
  9. G. Contestabile, A. Maruta, S. Sekiguchi, K. Morito, M. Sugawara, and K. Kitayama, “Regenerative Amplification by Using Self-Phase Modulation in a Quantum-Dot SOA,” IEEE Photon. Technol. Lett. 22(7), 492–494 (2010). [CrossRef]
  10. R. Bonk, C. Meuer, T. Vallaitis, S. Sygletos, P. Vorreau, S. Ben-Ezra, S. Tsadka, A. Kovsh, I. Krestnikov, M. Laemmlin, D. Bimberg, W. Freude, and J. Leuthold, “Single and Multiple Channel Operation Dynamics of Linear Quantum-Dot Semiconductor Optical Amplifier,” in European Conference on Optical Communications (ECOC 2008)(Brussels, Belgium, 2008), p. Th.1.C.2.
  11. C. Schmidt-Langhorst, C. Meuer, A. Galperin, H. Schmeckebier, R. Ludwig, D. Puris, D. Bimberg, K. Petermann, and C. Schubert, “80 Gb/s Multi-Wavelength Booster Amplification in an InGaAs/GaAs Quantum-Dot Semiconductor Optical Amplifier,” in European Conference on Optical Communication (ECOC 2010)(Torino, Italy, 2010), p. Mo.1.F.6.
  12. G. Contestabile, A. Maruta, S. Sekiguchi, K. Morito, M. Sugawara, and K. Kitayama, “Regenerative Amplification in a Quantum Dot SOA ” in Optical Fiber Communication Conference (OFC 2010)(San Diego, CA, USA, 2010), p. OMT2.
  13. T. Akiyama, N. Hatori, Y. Nakata, H. Ebe, and M. Sugawara, “Pattern-effect-free amplification and cross-gain modulation achieved by using ultrafast gain nonlinearity in quantum-dot semiconductor optical amplifiers,” Phys. Status Solidi, B Basic Res. 238(2), 301–304 (2003). [CrossRef]
  14. G. Contestabile, A. Maruta, S. Sekiguchi, K. Morito, and K. Kitayama, “80 Gb/s Multicast Wavelength Conversion by XGM in a QD-SOA,” in European Conference on Optical Communication (ECOC2010)(Torino, Italy, 2010), p. Mo.2.A.3.
  15. G. Contestabile, A. Maruta, S. Sekiguchi, K. Morito, M. Sugawara, and K. Kitayama, “160 Gb/s cross gain modulation in quantum dot SOA at 1550 nm,” in European Conference on Optical Communication (ECOC 2009)(Vienna, Austria, 2009), p. PDP 1.4.
  16. A. E. Kelly, A. D. Ellis, D. Nesset, R. Kashyap, and D. G. Moodie, “100Gbit/s wavelength conversion using FWM in an MQW semiconductor optical amplifier,” Electron. Lett. 34(20), 1955–1956 (1998). [CrossRef]
  17. U. Feiste, R. Ludwig, C. Schmidt, E. Dietrich, S. Diez, H. Ehrke, E. Patzak, H. G. Weber, and T. Merker, “80-Gb/s transmission over 106-km standard-fiber using optical phase conjugation in a Sagnac-interferometer,” IEEE Photon. Technol. Lett. 11(8), 1063–1065 (1999). [CrossRef]
  18. S. Diez, C. Schubert, H.-J. Ehrke, U. Feiste, R. Ludwig, E. Patzak, C. Schmidt, and H. G. Weber, “160 Gb/s all-optical demultiplexer using a hybrid gain-transparent SOA Mach-Zehnder-Interferometer,” Electron. Lett. 36(17), 1484 (2000). [CrossRef]
  19. S. L. Jansen, M. Heid, S. Spalter, E. Meissner, C. J. Weiske, A. Schopflin, D. Khoe, and H. de Waardt, “Demultiplexing 160 Gbit/s OTDM signal to 40 Gbit/s by FWM in SOA,” Electron. Lett. 38(17), 978–980 (2002). [CrossRef]
  20. T. Akiyama, H. Kuwatsuka, N. Hatori, Y. Nakata, H. Ebe, and M. Sugawara, “Symmetric Highly Efficient (~0 dB) Wavelength Conversion Based on Four-Wave Mixing in Quantum Dot Optical Amplifiers,” IEEE Photon. Technol. Lett. 14(8), 1139–1141 (2002). [CrossRef]
  21. A. Capua, S. O’Duill, V. Mikhelashvili, G. Eisenstein, J. P. Reithmaier, A. Somers, and A. Forchel, “Cross talk free multi channel processing of 10 Gbit/s data via four wave mixing in a 1550 nm InAs/InP quantum dash amplifier,” Opt. Express 16(23), 19072–19077 (2008). [CrossRef]
  22. D. Nielsen, S. L. Chuang, N. J. Kim, D. Lee, S. H. Pyun, and W. G. Jeong, “160 GHz wavelength conversion using four-wave mixing in quantum dots,” in Conference on Lasers and Electro-Optics (CLEO)(Baltimore, MD, USA, 2009).
  23. D. Bimberg, C. Meuer, M. Laemmlin, S. Liebich, J. Kim, A. R. Kovsh, I. Krestnikov, and G. Eisenstein, “Nonlinear properties of quantum dot semiconductor optical amplifiers at 1.3 µm,” Chin. Opt. Lett. 6, 724–726 (2008). [CrossRef]
  24. A. R. Kovsh, N. A. Maleev, A. E. Zhukov, S. S. Mikhrin, A. P. Vasil'ev, E. A. Semenova, Y. M. Shernyakov, M. V. Maximov, D. A. Livshits, V. M. Ustinov, N. N. Ledentsov, D. Bimberg, and Z. I. Alferov, “InAs/InGaAs/GaAs quantum dot lasers of 1.3 µm range with enhanced optical gain,” J. Cryst. Growth 251(1-4), 729–736 (2003). [CrossRef]
  25. C. Meuer, H. Schmeckebier, G. Fiol, D. Arsenijevic, J. Kim, G. Eisenstein, and D. Bimberg, “Cross-Gain Modulation and Four-Wave Mixing for Wavelength Conversion in undoped and p-doped 1.3 µm Quantum Dot Semiconductor Optical Amplifiers,” IEEE Photon. 2(2), 141–151 (2010). [CrossRef]
  26. A. Bilenca, R. Alizon, V. Mikhelashhvili, D. Dahan, G. Eisenstein, R. Schwertberger, D. Gold, J. P. Reithmaier, and A. Forchel, “Broad-band wavelength conversion based on cross-gain modulation and four-wave mixing in InAs-InP quantum-dash semiconductor optical amplifiers operating at 1550 nm,” IEEE Photon. Technol. Lett. 15(4), 563–565 (2003). [CrossRef]
  27. D. Nielsen, S. L. Chuang, N. J. Kim, D. Lee, S. H. Pyun, W. G. Jeong, C. Y. Chen, and T. S. Lay, “High-speed wavelength conversion in quantum dot and quantum well semiconductor optical amplifiers,” Appl. Phys. Lett. 92(21), 211101 (2008). [CrossRef]
  28. K. Kikuchi, M. Kakui, C. E. Zah, and T. P. Lee, “Observation of Highly Nondegenerate 4-Wave-Mixing in 1.5 µm Traveling-Wave Semiconductor Optical Amplifiers and Estimation of Nonlinear Gain Coefficient,” IEEE J. Quantum Electron. 28(1), 151–156 (1992). [CrossRef]
  29. A. E. Kelly, D. D. Marcenac, and D. Nesset, “40Gbit/s wavelength conversion over 24.6nm using FWM in a semiconductor optical amplifier with an optimised MQW active region,” Electron. Lett. 33(25), 2123–2124 (1997). [CrossRef]
  30. G. Grosskopf, R. Ludwig, and H. G. Weber, “140 Mbit/s DPSK Transmission Using an All-Optical Frequency-Converter with a 4000 GHz Conversion Range,” Electron. Lett. 24(17), 1106–1107 (1988). [CrossRef]
  31. N. Schunk, G. Groβkopt, R. Ludwig, R. Schnabel, and H. G. Weber, “Frequency-Conversion by Nearly-Degenerate 4-Wave-Mixing in Traveling-Wave Semiconductor-Laser Amplifiers,” IEE Proc. Optoelectron. 137, 209–214 (1990). [CrossRef]
  32. G. Contestabile, F. Martelli, A. Mecozzi, L. Graziani, A. D'Ottavi, P. Spano, G. Guekos, R. Dall'Ara, and J. Eckner, “Efficiency flattening and equalization of frequency up- and down-conversion using four-wave mixing in semiconductor optical amplifiers,” IEEE Photon. Technol. Lett. 10(10), 1398–1400 (1998). [CrossRef]
  33. T. J. Morgan, J. P. R. Lacey, and R. S. Tucker, “Widely tunable four-wave mixing in semiconductor optical amplifiers with constant conversion efficiency,” IEEE Photon. Technol. Lett. 10(10), 1401–1403 (1998). [CrossRef]
  34. I. Tomkos, I. Zacharopoulos, D. Syvridis, T. Sphicopoulos, and E. Roditi, “Improved performance of a wavelength converter based on dual pump four-wave mixing in a bulk semiconductor optical amplifier,” Appl. Phys. Lett. 72(20), 2499–2501 (1998). [CrossRef]
  35. S. Diez, C. Schmidt, R. Ludwig, H. G. Weber, K. Obermann, S. Kindt, I. Koltchanov, and K. Petermann, “Four-wave mixing in semiconductor optical amplifiers for frequency conversion and fast optical switching,” IEEE J. Sel. Top. Quantum Electron. 3(5), 1131–1145 (1997). [CrossRef]
  36. P. Borri, W. Langbein, J. M. Hvam, F. Heinrichsdorff, H.-M. Mao, and D. Bimberg, “Spectral Hole-Burning and Carrier-Heating Dynamics in InGaAs Quantum-Dot Amplifiers,” IEEE J. Sel. Top. Quantum Electron. 6(3), 544–551 (2000). [CrossRef]

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