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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 14 — Jul. 4, 2011
  • pp: 13540–13550
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Label swapper device for spectral amplitude coded optical packet networks monolithically integrated on InP

P. Muñoz, R. García-Olcina, C. Habib, L. R. Chen, X. J. M. Leijtens, T. de Vries, D. Robbins, and J. Capmany  »View Author Affiliations


Optics Express, Vol. 19, Issue 14, pp. 13540-13550 (2011)
http://dx.doi.org/10.1364/OE.19.013540


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Abstract

In this paper the design, fabrication and experimental characterization of an spectral amplitude coded (SAC) optical label swapper monolithically integrated on Indium Phosphide (InP) is presented. The device has a footprint of 4.8x1.5 mm2 and is able to perform label swapping operations required in SAC at a speed of 155 Mbps. The device was manufactured in InP using a multiple purpose generic integration scheme. Compared to previous SAC label swapper demonstrations, using discrete component assembly, this label swapper chip operates two order of magnitudes faster.

© 2011 OSA

1. Introduction

Fig. 1 Spectral Amplitude Coded (SAC) label time and wavelength domain representations.

All in all, the label is a number represented by a stream of bits (which are represented in wavelength). Swapping labels means changing the state of some or all the bits. Thus, the optical implementation requires the ability to perform several digital logic operations in the optic domain, in particular NAND and NOR gating. In SAC labeling this translates into being able to perform these operations on a per wavelength basis at a few hundred Mbps. SAC swapping devices using cross-gain modulation (XGM) in ring cavities have previously been demonstrated with high extinction and contrast ratios [7

7. R. Gordon and L. Chen, “Demonstration of all-photonic spectral label-switching for optical MPLS networks,” IEEE Photon. Technol. Lett. 18, 586–588 (2006). [CrossRef]

]. In particular, a proof-of-concept tabletop (2x1 m2) label-swapper using a two stage XGM-based fiber-ring laser has been demonstrated in [8

8. C. Habib, V. Baby, L. Chen, A. Delisle-Simard, and S. LaRochelle, “All-optical swapping of spectral amplitude code labels using nonlinear media and semiconductor fiber ring lasers,” IEEE J. Sel. Top. Quantum Electron. 14, 879–888 (2008). [CrossRef]

]. The main drawbacks of this device were cost and low operating frequency (80 kHz) due to a lengthy cavity (8.9 m). In [12

12. N. Calabretta, J. Hyun-Do, J. Llorente, E. Tangdiongga, T. Koonen, and H. Dorren, “All-optical label swapping of scalable in-band address labels and 160-Gb/s data packets,” J. Lightwave Technol. 27, 214–223 (2009). [CrossRef]

] a different SAC label swapper implementation using a Semiconductor Optical Amplifier-Mach Zehnder Interferometer (SOA-MZI) was demonstrated at a label rate of 4 MHz, according to the packet payload duration (256 ns, payload rate 160 Gbps). Both SAC swapping devices were constructed by assembling a large number of discrete components. A practical cost-effective implementation requires small footprint in the form of photonic integrated circuits [9

9. C. Cole, B. Huebner, and J. Johnson, “Photonic integration for high-volume, low-cost applications,” IEEE Commun. Mag. 47, S16–S22 (2009). [CrossRef]

]. We thus present, a photonic integrated circuit that performs parallel per-wavelength digital logic operations required in a SAC label swapping node. The circuit is monolithically integrated in Indium Phosphide (InP) technology [10

10. E. Bente and M. Smit, “Ultrafast InP optical integrated circuits,” in Optoelectronic Integrated Circuits VIII, L.A. Eldada and E.-H. Lee, eds., Proc. SPIE 6124, 612419 (2006).

], using a multiple purpose generic integration scheme [11

11. X. Leijtens, “JePPIX: the platform for InP-based photonics,” in Proceedings of the 15th European Conference on Integrated Optics (ECIO, 2010), pp. ThG3–1/2.

], hence compatible with state of the art commercial components for optical communications. The circuit operation speed is two orders of magnitude higher than in [12

12. N. Calabretta, J. Hyun-Do, J. Llorente, E. Tangdiongga, T. Koonen, and H. Dorren, “All-optical label swapping of scalable in-band address labels and 160-Gb/s data packets,” J. Lightwave Technol. 27, 214–223 (2009). [CrossRef]

], with a footprint five orders of magnitude smaller, than the previously reported equivalent subsystems [8

8. C. Habib, V. Baby, L. Chen, A. Delisle-Simard, and S. LaRochelle, “All-optical swapping of spectral amplitude code labels using nonlinear media and semiconductor fiber ring lasers,” IEEE J. Sel. Top. Quantum Electron. 14, 879–888 (2008). [CrossRef]

].

This paper is structured as follows: in section 2, the design of the device is described. Section 3 is devoted to the description of two operation modes, with focus on the results. Hence, and for clarity on the device operation, the details on the experiments, and on the fabrication technology are provided separately in section 4. Finally, the conclusions are drawn in section 5.

2. Device design

The device is based on a linear multi-wavelength laser configuration [13

13. J. den Besten, “Integration of multiwavelength lasers with fast electro-optical modulators,” Ph.D. thesis, TU Eindhoven (2004).

], built using several Sagnac Loop Reflectors (SLR) [14

14. B. Saleh and M. Teich, Fundamentals of Photonics (Wiley, 2007), Chap. 2.

], one Arrayed Waveguide Grating (AWG) [15

15. M. Smit and C. Van Dam, “PHASAR-based WDM-devices: principles, design and applications,” IEEE J. Sel. Top. Quantum Electron. 2, 236–250 (1996). [CrossRef]

] and several Semiconductor Optical Amplifiers (SOAs) [16

16. G. Eisenstein, “Semiconductor Optical Amplifiers,” IEEE Circuits Devices Mag. 5, 25–30 (1989). [CrossRef]

] on a single InP chip. A micro-graph of the device is provided in Fig. 2-(a) [17

17. P. Munñoz, R. Garcia-Olcina, J. D. Domenech, M. Rius, J. Capmany, L. R. Chen, C. Habib, X. J. M. Leijtens, T. de Vries, M. R. Heck, L. M. Augustin, R. Nötzel, and D. J. Robbins, “Multi-wavelength lasers based on an arrayed waveguide grating and Sagnac loop reflectors monolithically integrated on InP,” in Proceedings of the 15th European Conference on Integrated Optics (ECIO, 2010), pp. WeF2–1/2.

]. The device is a linear laser between the SLRs enclosing SOA2-AWG-SOA Li i=1...4, where the SOA2 acts a common cavity gain medium, and the AWG and SOA Li combination enable the different output wavelengths/labels. The light is out-coupled from the laser cavity using a side diffraction order of the AWG [18

18. P. Munoz, D. Pastor, and J. Capmany, “Modeling and design of arrayed waveguide gratings,” J. Lightwave Technol. 20, 661–674 (2002). [CrossRef]

], denoted ’FSR out coup’ in the figure, through the waveguide named ’2’ in the figure. An additional waveguide, denoted ’1’, at the SOA Li side is laid out as input for the incoming labels, through SOA1 that can be used as pre-amplifier. This waveguide extends also directly to the right hand side of the chip -by mean of a coupler-, denoted ’3’ in the figure, and it is used for complimentary purposes (reference, alignment and control).

Fig. 2 Device micro graph, inputs/outputs 1, 2, 3 and SOA’s labeled (a) and characterization setups (b)(c) (TL Tunable Laser, PC Polarization Controller, EOM Electro-Optic Modulator, RFA Radio-Frequency Amplifier, PRBS Pseudo Random Bit Sequence generator, EDFA Erbium Doped Fiber Amplifier, VOA Variable Optical Attenuator, LS Label Swapper chip, LDD Laser Diode Driver, OSA Optical Spectrum Analyzer, FBG Fiber Bragg Grating, CSA Communications Signal Analyzer).

The AWG was designed to work at λ 0=1550 nm, with 2 input and 5 output spectral channels spaced Δλc= 1.6 nm. The design is for a cyclic response, FSR=5*1.6=8 nm, and for two diffraction orders [18

18. P. Munoz, D. Pastor, and J. Capmany, “Modeling and design of arrayed waveguide gratings,” J. Lightwave Technol. 20, 661–674 (2002). [CrossRef]

] to be available at the input/output slab couplers. Hence 50:50 out coupling from the laser cavity can be performed without the need of an additional power splitter, since input waveguides have the same spectral transfer function, as labeled in Fig. 2-(a) as ’FSR out-coup’. The loop reflectors are Sagnac interferometers with a 2x2 MMI coupler [19

19. L. Soldano and E. Pennings, “Optical multi-mode interference devices based on self-imaging: principles and applications,” J. Lightwave Technol. 13, 615–627 (1995). [CrossRef]

] that provides a π/2 phase shift between the two outputs, necessary for total reflection [14

14. B. Saleh and M. Teich, Fundamentals of Photonics (Wiley, 2007), Chap. 2.

]. Although just one waveguide in the Sagnac is used, the other one is terminated in a pigtail/spiral shaped waveguide, Fig. 2-(a), to minimize unwanted reflections due to possible imperfections. The SOA sections have a length of 500 μm. The amplifiers SOA2 and SOA’s Li, i=1..4, are used to obtain sufficient gain for lasing to occur at each cavity. Additionally, thermo-optic heaters are laid between the SOAs and the Sagnacs, to control the cavity phase. The designed Fabry-Perot cavity length between SLRs is 6.7 mm, which is the determinant feature in the operation speed.

3. Device characterization

3.1. Overview

Without the event of incoming signals to the swapper, the device works as a regular multi-wavelength laser [13

13. J. den Besten, “Integration of multiwavelength lasers with fast electro-optical modulators,” Ph.D. thesis, TU Eindhoven (2004).

]. However, when incoming signals/labels are used as inputs, with proper wavelengths, the device lasing operation can be optically controlled. In particular, if the input signals are encoded in amplitude, logical operations can be performed.

Two sets of experiments were conducted, both with similar equipment detailed in Fig. 2-(b) and (c). Each experiment demonstrates a different operation mode. The first operation mode, described in section 3.2, demonstrates swapping from one input wavelength to one or many, but simultaneous, output wavelengths. The second operation mode, section 3.3, shows the operation from a set of input to a set of output wavelengths, with pairs of input/output wavelength operating independently.

In both experiments, tunable lasers (TL) were used to provide the input signals. Variable Optical Attenuators (VOAs) were employed to set their power levels to the appropriate operating point on the device input vs. output power static transfer function, with the TLs being operated in Continuous Wave (CW) mode. The static operation curves were obtained from the peaks measured in the traces acquired by means of an Optical Spectrum Analyzer (OSA). In the first set of experiments based on the setup illustrated in Fig. 2-(b), the maximum operational speed, i.e., the label rate, was assessed by using the additional hardware shown within dashed boxes. A pseudo-random bit sequence (PRBS) generator provided the digital pulses, Non-Return to Zero (NRZ), to modulate the amplitude of the CW TLs by means of an Electro-Optical Modulator (EOM). A Communications Signal Analyzer (CSA) was then used to measure the quality factor (Q) of the signal returned from the chip.

3.2. Single input wavelength operation

The device was operated using waveguides ’1’ and ’2’ as input and output respectively, as detailed in Fig. 2-(b). Referring also to Fig. 2-(a), the output lasing wavelengths were enabled at ’2’ by biasing SOA2 and SOAs Li (dashed white and color lines). Next, an external laser signal with proper wavelength to reach SOA2 through the AWG was used as input in ’1’ (dashed black line). The SOAs biases were adjusted to allow switching on and off the on chip lasing by turning off and on the input, so the output is an inverted version of the input.

The single input to single output static transfer function curves are shown in Fig. 3-(a). The traces are shown in the same colors as the ones used to mark the lasing cavities in Fig. 2-(a). The graphs and caption detail how the input signal is translated in wavelength and inverted in amplitude to the output. Moreover, the input signal was modulated with a PRBS generator operated at 155 Mbps. This operation rate is 2 orders of magnitude higher than similar SAC label swapping experiments reported with non-integrated devices (4 Mbps) [12

12. N. Calabretta, J. Hyun-Do, J. Llorente, E. Tangdiongga, T. Koonen, and H. Dorren, “All-optical label swapping of scalable in-band address labels and 160-Gb/s data packets,” J. Lightwave Technol. 27, 214–223 (2009). [CrossRef]

], hence allowing for higher label rates and/or shorter guard times (i.e., less overhead). The quality factor of the converted digital signal is shown in Fig. 3-(b). The insets provide screen-shots of the digital eye patterns at the marked operation points in the static curves, b1, b2 and b3. Quality factors greater than 6, corresponding to a bit error rate (BER) smaller than 10−9, were attained. The extinction ratio measured back to back for the equivalent average power was between 10 and 11 dB for an average power in [−6,−3] dBm. In this range, the measured extinction ratio for SOAs L1 to L4 was in [4

4. D. Blumenthal, B.-E. Olsson, G. Rossi, T. Dimmick, L. Rau, M. Masanovic, O. Lavrova, R. Doshi, O. Jerphagnon, J. Bowers, V. Kaman, L. Coldren, and J. Barton, “All-optical label swapping networks and technologies,” J. Lightwave Technol. 18, 2058–2075 (2000). [CrossRef]

, 14

14. B. Saleh and M. Teich, Fundamentals of Photonics (Wiley, 2007), Chap. 2.

] dB, [2

2. S. J. B. Yoo, “Optical packet and burst switching technologies for the future photonic Internet,” J. Lightwave Technol. 24, 4468–4492 (2006). [CrossRef]

,4

4. D. Blumenthal, B.-E. Olsson, G. Rossi, T. Dimmick, L. Rau, M. Masanovic, O. Lavrova, R. Doshi, O. Jerphagnon, J. Bowers, V. Kaman, L. Coldren, and J. Barton, “All-optical label swapping networks and technologies,” J. Lightwave Technol. 18, 2058–2075 (2000). [CrossRef]

] dB, [2

2. S. J. B. Yoo, “Optical packet and burst switching technologies for the future photonic Internet,” J. Lightwave Technol. 24, 4468–4492 (2006). [CrossRef]

,6

6. P. Seddighian, J. Rosas-Fernández, S. Ayotte, L. Rusch, S. Larochelle, and A. Leon-Garcia, “Low-cost scalable optical packet switching networks with multi-wavelength labels,” in Proc. OFC/NFOEC (2007), paper OthF5.

] dB and [4

4. D. Blumenthal, B.-E. Olsson, G. Rossi, T. Dimmick, L. Rau, M. Masanovic, O. Lavrova, R. Doshi, O. Jerphagnon, J. Bowers, V. Kaman, L. Coldren, and J. Barton, “All-optical label swapping networks and technologies,” J. Lightwave Technol. 18, 2058–2075 (2000). [CrossRef]

,13

13. J. den Besten, “Integration of multiwavelength lasers with fast electro-optical modulators,” Ph.D. thesis, TU Eindhoven (2004).

] dB respectively.

Fig. 3 Experimental results with setup A, Fig. 2-(b). Input through chip input ‘1’ at wavelength 1561.8 nm, chip output ‘2’ at wavelengths for SOA Li i=1,2,3,4: 1576.30 nm, 1574.61 nm, 1573.01 nm and 1571.32 nm respectively. The colors correspond to those of Fig. 2-(a). Sub-figures (a) and (b) represent the static (CW in/out) and dynamic (modulated in/out) operation of the device, whilst (c) and (d) represent the static and dynamic operation for one input and two simultaneous outputs. The insets in the dynamic traces (b) and (d) are the eye pattern diagrams (155 Mbps if otherwise not indicated), for which the operation point is correspondingly marked in the static curves (a) and (c). All the power values refer to on-chip average power.

The operation was also tested with the PRBS operated at 622 Mbps, as shown in the dashed inset within Fig. 3-(b). Though significant bit patterning effects can be observed due to the carrier recovery time associate with these particular SOAs, Q factors greater than 6 were still obtained.

A single input can also be mapped to several outputs. The static and dynamic (155 Mbps) results, are shown in Fig. 3-(c) and (d) respectively, when two outputs are enabled at the same time. This can be of use when one input bit is used to reset or set more than one output bit. The results are only presented for two simultaneous outputs. In the configuration of Fig. 2-(b) it is also possible to enable the four wavelengths at the same time. However, as detailed in [17

17. P. Munñoz, R. Garcia-Olcina, J. D. Domenech, M. Rius, J. Capmany, L. R. Chen, C. Habib, X. J. M. Leijtens, T. de Vries, M. R. Heck, L. M. Augustin, R. Nötzel, and D. J. Robbins, “Multi-wavelength lasers based on an arrayed waveguide grating and Sagnac loop reflectors monolithically integrated on InP,” in Proceedings of the 15th European Conference on Integrated Optics (ECIO, 2010), pp. WeF2–1/2.

], for the four lasers to have wavelengths within the same AWG FSR, the needed bias currents were as high as to disallow on/off switching with the input wavelength/label. This might be solved in forthcoming designs by improving the overall architecture to minimize waveguide propagation, device insertion and fiber in/out coupling losses. Moreover, mode-hopping between the AWG side modes takes place in this particular device when more than two wavelengths are used. This disallows dynamic operation, as a filter is employed before the BER analyzer. The mode hopping can also be prevented using more aggressive designs for the AWG, i.e. with narrower channel bandwidth and larger FSR [13

13. J. den Besten, “Integration of multiwavelength lasers with fast electro-optical modulators,” Ph.D. thesis, TU Eindhoven (2004).

].

3.3. Parallel input wavelength operation

Fig. 4 Experimental results with setup B, Fig. 2-(c). The input wavelengths to SOA Li, i=1,2,3 and 4 are, respectively: 1559.77 nm, 1558.13 nm, 1556.58 nm and 1554.94 nm, output wavelengths as in setup A. The colors correspond to those of Fig. 2-(a). Sub-figure (a) presents the 4 input to 4 output CW operation, and the inset OSA traces correspond to Pin = – 30 dBm/0.1 nm/channel -magenta- and Pin = 0 dBm/0.1 nm/channel -pink-. OSA traces (b)(c) and (d) show different 4 bit input/output combinations. Markers on the OSA traces match those of the figure. Arrows for the input wavelengths are used, each in the color corresponding to their associated output. All the power values refer to on-chip average power.

4. Materials and methods

4.1. Experiment details

The device was soldered to a copper chuck and its temperature was kept at 25 C during the measurements by means of a Peltier cell. The the chuck holder was water-cooled to dissipate the heat produced by the current injection in the active areas of the chip. A multi-contact wedge was used to probe the SOA’s, and a lensed fiber was aligned with the output waveguide using a nano-positioning stage. Prior to any system measurement, the FP cavity length was confirmed by measuring the multi-wavelength laser spectra with a 10 pm resolution OSA. The FP mode spacing resulted in 51.4 pm, corresponding to the cavity length of 6.7 mm with an average group index of 3.5. The waveguide losses (5 dB/cm) and lensed fiber in/out coupling losses (6 dB) were measured through test structures. The AWG insertion loss was 8.5 dB. The waveguides in the arms of the AWG were designed as deeply etched [10

10. E. Bente and M. Smit, “Ultrafast InP optical integrated circuits,” in Optoelectronic Integrated Circuits VIII, L.A. Eldada and E.-H. Lee, eds., Proc. SPIE 6124, 612419 (2006).

] of 1.5 μm width, aiming at matching TE and TM effective indexes. The SOAs structure provides gain for TE polarization.

In setup A, Fig. 2-(b), the external light source was a tunable laser model IQS-2400 from EXFO, emitting +8 dBm at 1561.81 nm. This wavelength corresponds to one of the AWG pass bands, therefore it can pass through the AWG and reach the SOA2, Fig. 2-(a). The polarization of the external laser light was rotated before feeding the electro-optical modulator from Avanex (up to 10 Gbps) by means of a manual polarization controller from Fiberpro, in order to maximize the modulation efficiency. The modulator was driven by a 155 Mbps PRBS digital signal coming from a SONET/SDH test module model OTS9100 from Tektronix, and amplified by an RF electrical amplifier model SA1137 from WJ Communications. For the static curves, the electrical amplifier was powered off, so the external laser signal was not digitally modulated.

For the static measurements, the output signal from ’2’, Fig. 2-(a), was measured using a Optical Spectrum Analyzer (OSA) from HP model 70951A with a resolution of 0.1 nm. The static curves, Fig. 3-(a), were obtained by varying the on-chip input power by means of the VOA and acquiring the peak data by a custom software developed in LabVIEW™.

To obtain the dynamic curves, the electrical amplifier was switched on and fed with a digital signal at 155 Mbps from the PRBS generator. A fiber Bragg grating (FBG) designed and fabricated in the Optical and Quantum Communications Group (OQCG) facilities at the Universidad Politecnica de Valencia, was connected at the chip output in reflective configuration, and mechanically tuned in order to isolate the wavelength of interest while filtering out the ASE noise from the EDFA. The grating was fabricated irradiating intrinsically photosensitive fiber PS1250/1500 from Fibercore™with a 500 μm wide spot of 244 nm UV light and using a novel FBG fabrication technique developed at the OQCG [24

24. R. Garcia-Olcina, “Sistema de fabricacion de altas prestaciones de redes de difraccion de Bragg en fibra y aplicaciones al campo de los sensores opticos y a los sistemas de comunicaciones opticas,” Ph.D. thesis, Universitat Politecnica Valencia (2008).

]. By this technique a 5-cm long Gaussian apodized FBG was fabricated employing a single 1 cm long uniform phase mask from Ibsen Photonics™. The peak refractive index variation was of 7e-5, producing an spectral response with a transmission at peak wavelength of −18 dB, and a 3 dB-bandwidth of 0.1 nm. The single-wavelength digitally modulated optical signal was then characterized by a Communication Signal Analyzer model DSA8200 from Tektronix, and different signal quality parameters, as Q factor, were obtained.

In setup B, Fig. 2-(c), the external light sources were four tunable lasers model IQS-2400 from EXFO, emitting +10 dBm at 1554.94 nm, 1556.58 m, 1558.13 nm and 1559.77 nm, respectively. The light was injected and collected by the port ’2’ using an optical circulator. These wavelengths correspond again to the AWG pass bands, therefore the four external signals can pass through the AWG and reach the four corresponding SOAs Li, Fig. 2-(a). As mentioned before, the optical properties of the integrated SOAs showed a strong dependence on the polarization state of the input signal, so the polarization of the external lasers were individually rotated before being combined by a passive 4x1 coupler by means of four manual polarization controllers, in order to align the polarization state of each external laser signals and the polarization state of the spontaneous emission from their corresponding SOA Li. No additional polarization controller was used before the chip, but high care in stabilizing fiber pigtails and connection on the optical table was taken.

To set up the proper operation point, the SOAs Li and SOA2 were contacted by electric probes and electrically biased in such a way that the internal Li lasers switched between on and off states when the corresponding external signals from EXFO lasers were injected in the chip. Note that in this case the XGM effect takes place in every individual SOA Li instead of in SOA2 as in setup A, so the electrical currents for the proper operation were different. The electrical current values in this case were IL1 = 36.9 mA, IL2 = 28.1 mA, IL3 = 25.4 mA, IL4 = 28.5 mA and ISOA2 = 30 mA. The SOA1 was not used in this configuration. Due to the XGM effect in each SOA Li, when the corresponding external lasers were enabled the SOA Li gain was saturated and that caused that internal laser Li was switched off, and vice versa.

4.2. Fabrication details

The label-swapper device has been fabricated using an integration technology based on InP/InGaAsP. This technology is able to produce integrated optical circuits that can contain devices built up from active and passive waveguide elements. The passive waveguides can be low contrast (shallowly etched) waveguides or high contrast (deeply etched) waveguides. Both types can be realized on the same chip using Reactive Ion Etching [13

13. J. den Besten, “Integration of multiwavelength lasers with fast electro-optical modulators,” Ph.D. thesis, TU Eindhoven (2004).

] and several masking steps. By using a suitable doping profile in the top layers and applying a metal contact on the top of the passive waveguide an electro-optic phase modulator can be realized [13

13. J. den Besten, “Integration of multiwavelength lasers with fast electro-optical modulators,” Ph.D. thesis, TU Eindhoven (2004).

]. Due to the fact that in this semiconductor system both the refractive indexes (> 3) and the contrast are high, the light is tightly confined and therefore the radius of curvature of curved waveguides can be small. In our design, the minimum radius of curvature of deeply etched passive waveguides was limited to 100 μm, so a relatively complex subsystem, such as this label-swapper, which includes several components (one AWG, five Sagnac mirrors, six SOAs and 3 input/output waveguides) has a footprint as small as 4.8 × 1.5 mm2.

Additionally, active devices such as optical amplifiers and saturable absorbers can be realized in predefined areas which have an active layer stack on the chip. These active areas are made using a selective area regrowth technique. The layers are grown by Metal-Organic Vapour Phase Epitaxy (MOVPE) with all metal-organic precursors in a three-step process. In the first epitaxy step, a 500 nm thick active film is grown, that provides optical confinement and gain. This film consists of 190 nm quaternary InGaAsP material (Q1.25, λ bandgap = 1.25 μm), a 120 nm Q1.55 layer providing the gain, and a 190 nm Q1.25 layer. In addition, the first 200 nm p-doped InP top cladding layer is grown. A SiNx mask layer is deposited by Plasma-Enhanced Chemical Vapour Deposition (PECVD) and patterns of active regions that are 30 μm wide with a length ranging from 20 to 2000 μm are defined by photolithography and etched into the SiNx. Outside the masked regions, the layers are removed down to the first Q1.25 layer, with a combination of dry and wet etching that leaves an overhang in the SiNx mask. Then a 500 nm thick passive undoped Q1.25 waveguide layer and a 200 nm undoped InP cladding is selectively grown outside the masked regions. The overhang in the mask ensures a flat surface and a low-loss butt-joint between the active and passive areas. Subsequently, the SiNx mask is removed and a common 1300 nm thick, p-doped InP top layer with gradually increasing doping level is grown on both the passive and active regions, with a highly p-doped ternary InGaAs contact layer on top. Local planarisation with polyimide is used that also provides passivation of the active waveguide. A Ti-Pt-Au metallisation scheme is applied, which was selected because it provides low-resistance ohmic contacts to both the p-doped InGaAs and the n-doped InP layers.

Shallowly etched active waveguides are fabricated in the active layer regions. The analysis of sub-threshold spectra of extended cavity lasers shows that reflections of transitions from the passive to the active (amplifying) areas in shallow waveguides at the butt-joint interface can be kept at −50 dB or less [20

20. Y. Barbarin, E. Bente, T. de Vries, J. den Besten, P. van Veldhoven, M. Sander-Jochem, E. Smalbrugge, F. van Otten, E. Geluk, M. Heck, X. Leijtens, J. van der Tol, F. Karouta, Y. Oei, R. Notzel, and M. Smit, “Butt-joint interfaces in InP/InGaAsP waveguides with very low reflectivity and low loss,” in Proc. Symposium IEEE/LEOS Benelux Chapter, (IEEE, 2005).

]. This is particularly relevant for this label-swapper subsystem since feedback above −50 dB can seriously affect the behavior of the laser system.

5. Discussion and conclusion

Other important issue is the optical power balance, which is to be improved, as on chip power at the input/output. This figure can be improved (less input power required to switch, more output power) for instance by means of spot size converters, for a more efficient light in/out coupling (0.5 dB at [23

23. F. Soares, F. Karouta, E. Geluk, J. Zantvoort, H. de Waardt, R. Baets, and M. Smit, “Low-loss InP-based spot-size converter based on a vertical taper,” in Proceedings of the 15th European Conference on Integrated Optics (ECIO, 2005), pp. 104–107.

]), and/or by including an additional integrated SOA as booster amplifier for the output signal.

Finally, besides the particular and relevant application of the device demonstrated in this paper, the concept and functionality can serve other purposes. In general, the device can be operated as logical NAND or NOR gate through wavelength conversion, but at very modest rate (hundreds of Mbps) compared to other photonic integrated converters based on SOA-MZI, that can be found in the literature elsewhere.

Acknowledgments

The activities have been carried out in the framework of the Joint Research Activity (JRA) ’Active-phased Arrayed Devices’ (WP 44) of the European Commission FP6 Network of Excellence ePIXnet (European Network of Excellence on Photonic Integrated Components and Circuits), Project Reference: 004525, http://www.epixnet.org/. This work has been partially funded through the Spanish Plan Nacional de I+D+i 2008–2011 project TEC2008-06145/TEC. It has also been partially supported by the Canadian Institute for Photonic Innovations. Devices are presently being fabricated through the InP Photonic Integration Platform JePPIX (coordinator D J Robbins), at the COBRA fab, http://www.jeppix.eu/

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R. Bolla, R. Bruschi, F. Davoli, and F. Cucchietti, “Energy efficiency in the future Internet: a survey of existing approaches and trends in energy-aware fixed network infrastructures,” IEEE Commun. Surv. Tutorials PP, 1–22 (2010).

4.

D. Blumenthal, B.-E. Olsson, G. Rossi, T. Dimmick, L. Rau, M. Masanovic, O. Lavrova, R. Doshi, O. Jerphagnon, J. Bowers, V. Kaman, L. Coldren, and J. Barton, “All-optical label swapping networks and technologies,” J. Lightwave Technol. 18, 2058–2075 (2000). [CrossRef]

5.

A. Srivatsa, H. de Waardt, M. Hill, G. Khoe, and H. Dorren, “All-optical serial header processing based on two-pulse correlation,” Electron. Lett. 37, 234–235 (2001). [CrossRef]

6.

P. Seddighian, J. Rosas-Fernández, S. Ayotte, L. Rusch, S. Larochelle, and A. Leon-Garcia, “Low-cost scalable optical packet switching networks with multi-wavelength labels,” in Proc. OFC/NFOEC (2007), paper OthF5.

7.

R. Gordon and L. Chen, “Demonstration of all-photonic spectral label-switching for optical MPLS networks,” IEEE Photon. Technol. Lett. 18, 586–588 (2006). [CrossRef]

8.

C. Habib, V. Baby, L. Chen, A. Delisle-Simard, and S. LaRochelle, “All-optical swapping of spectral amplitude code labels using nonlinear media and semiconductor fiber ring lasers,” IEEE J. Sel. Top. Quantum Electron. 14, 879–888 (2008). [CrossRef]

9.

C. Cole, B. Huebner, and J. Johnson, “Photonic integration for high-volume, low-cost applications,” IEEE Commun. Mag. 47, S16–S22 (2009). [CrossRef]

10.

E. Bente and M. Smit, “Ultrafast InP optical integrated circuits,” in Optoelectronic Integrated Circuits VIII, L.A. Eldada and E.-H. Lee, eds., Proc. SPIE 6124, 612419 (2006).

11.

X. Leijtens, “JePPIX: the platform for InP-based photonics,” in Proceedings of the 15th European Conference on Integrated Optics (ECIO, 2010), pp. ThG3–1/2.

12.

N. Calabretta, J. Hyun-Do, J. Llorente, E. Tangdiongga, T. Koonen, and H. Dorren, “All-optical label swapping of scalable in-band address labels and 160-Gb/s data packets,” J. Lightwave Technol. 27, 214–223 (2009). [CrossRef]

13.

J. den Besten, “Integration of multiwavelength lasers with fast electro-optical modulators,” Ph.D. thesis, TU Eindhoven (2004).

14.

B. Saleh and M. Teich, Fundamentals of Photonics (Wiley, 2007), Chap. 2.

15.

M. Smit and C. Van Dam, “PHASAR-based WDM-devices: principles, design and applications,” IEEE J. Sel. Top. Quantum Electron. 2, 236–250 (1996). [CrossRef]

16.

G. Eisenstein, “Semiconductor Optical Amplifiers,” IEEE Circuits Devices Mag. 5, 25–30 (1989). [CrossRef]

17.

P. Munñoz, R. Garcia-Olcina, J. D. Domenech, M. Rius, J. Capmany, L. R. Chen, C. Habib, X. J. M. Leijtens, T. de Vries, M. R. Heck, L. M. Augustin, R. Nötzel, and D. J. Robbins, “Multi-wavelength lasers based on an arrayed waveguide grating and Sagnac loop reflectors monolithically integrated on InP,” in Proceedings of the 15th European Conference on Integrated Optics (ECIO, 2010), pp. WeF2–1/2.

18.

P. Munoz, D. Pastor, and J. Capmany, “Modeling and design of arrayed waveguide gratings,” J. Lightwave Technol. 20, 661–674 (2002). [CrossRef]

19.

L. Soldano and E. Pennings, “Optical multi-mode interference devices based on self-imaging: principles and applications,” J. Lightwave Technol. 13, 615–627 (1995). [CrossRef]

20.

Y. Barbarin, E. Bente, T. de Vries, J. den Besten, P. van Veldhoven, M. Sander-Jochem, E. Smalbrugge, F. van Otten, E. Geluk, M. Heck, X. Leijtens, J. van der Tol, F. Karouta, Y. Oei, R. Notzel, and M. Smit, “Butt-joint interfaces in InP/InGaAsP waveguides with very low reflectivity and low loss,” in Proc. Symposium IEEE/LEOS Benelux Chapter, (IEEE, 2005).

21.

C. E. Spurgeon, Ethernet: The Definitive Guide (O’Reilly & Associates, Inc., 2000).

22.

A. Zilkie, J. Meier, M. Mojahedi, P. Poole, P. Barrios, D. Poitras, T. Rotter, C. Yang, A. Stintz, K. Malloy, P. Smith, and J. Aitchison, “Carrier dynamics of quantum-dot, quantum-dash, and quantum-well semiconductor optical amplifiers operating at 1.55 μm,” IEEE J. Quantum Electron. 43, 982–991 (2007). [CrossRef]

23.

F. Soares, F. Karouta, E. Geluk, J. Zantvoort, H. de Waardt, R. Baets, and M. Smit, “Low-loss InP-based spot-size converter based on a vertical taper,” in Proceedings of the 15th European Conference on Integrated Optics (ECIO, 2005), pp. 104–107.

24.

R. Garcia-Olcina, “Sistema de fabricacion de altas prestaciones de redes de difraccion de Bragg en fibra y aplicaciones al campo de los sensores opticos y a los sistemas de comunicaciones opticas,” Ph.D. thesis, Universitat Politecnica Valencia (2008).

OCIS Codes
(060.1155) Fiber optics and optical communications : All-optical networks
(060.4259) Fiber optics and optical communications : Networks, packet-switched
(130.4815) Integrated optics : Optical switching devices
(130.6622) Integrated optics : Subsystem integration and techniques
(130.7405) Integrated optics : Wavelength conversion devices
(250.5960) Optoelectronics : Semiconductor lasers

ToC Category:
Integrated Optics

History
Original Manuscript: May 9, 2011
Revised Manuscript: June 14, 2011
Manuscript Accepted: June 14, 2011
Published: June 28, 2011

Citation
P. Muñoz, R. García-Olcina, C. Habib, L. R. Chen, X. J. M. Leijtens, T. de Vries, D. Robbins, and J. Capmany, "Label swapper device for spectral amplitude coded optical packet networks monolithically integrated on InP," Opt. Express 19, 13540-13550 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-14-13540


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References

  1. “Cisco visual networking index: forecast and methodology, 2009–2014,” White Paper, Cisco Networks (2010).
  2. S. J. B. Yoo, “Optical packet and burst switching technologies for the future photonic Internet,” J. Lightwave Technol. 24, 4468–4492 (2006). [CrossRef]
  3. R. Bolla, R. Bruschi, F. Davoli, and F. Cucchietti, “Energy efficiency in the future Internet: a survey of existing approaches and trends in energy-aware fixed network infrastructures,” IEEE Commun. Surv. Tutorials PP, 1–22 (2010).
  4. D. Blumenthal, B.-E. Olsson, G. Rossi, T. Dimmick, L. Rau, M. Masanovic, O. Lavrova, R. Doshi, O. Jerphagnon, J. Bowers, V. Kaman, L. Coldren, and J. Barton, “All-optical label swapping networks and technologies,” J. Lightwave Technol. 18, 2058–2075 (2000). [CrossRef]
  5. A. Srivatsa, H. de Waardt, M. Hill, G. Khoe, and H. Dorren, “All-optical serial header processing based on two-pulse correlation,” Electron. Lett. 37, 234–235 (2001). [CrossRef]
  6. P. Seddighian, J. Rosas-Fernández, S. Ayotte, L. Rusch, S. Larochelle, and A. Leon-Garcia, “Low-cost scalable optical packet switching networks with multi-wavelength labels,” in Proc. OFC/NFOEC (2007), paper OthF5.
  7. R. Gordon and L. Chen, “Demonstration of all-photonic spectral label-switching for optical MPLS networks,” IEEE Photon. Technol. Lett. 18, 586–588 (2006). [CrossRef]
  8. C. Habib, V. Baby, L. Chen, A. Delisle-Simard, and S. LaRochelle, “All-optical swapping of spectral amplitude code labels using nonlinear media and semiconductor fiber ring lasers,” IEEE J. Sel. Top. Quantum Electron. 14, 879–888 (2008). [CrossRef]
  9. C. Cole, B. Huebner, and J. Johnson, “Photonic integration for high-volume, low-cost applications,” IEEE Commun. Mag. 47, S16–S22 (2009). [CrossRef]
  10. E. Bente and M. Smit, “Ultrafast InP optical integrated circuits,” in Optoelectronic Integrated Circuits VIII , L.A. Eldada and E.-H. Lee, eds., Proc. SPIE 6124, 612419 (2006).
  11. X. Leijtens, “JePPIX: the platform for InP-based photonics,” in Proceedings of the 15th European Conference on Integrated Optics (ECIO, 2010), pp. ThG3–1/2.
  12. N. Calabretta, J. Hyun-Do, J. Llorente, E. Tangdiongga, T. Koonen, and H. Dorren, “All-optical label swapping of scalable in-band address labels and 160-Gb/s data packets,” J. Lightwave Technol. 27, 214–223 (2009). [CrossRef]
  13. J. den Besten, “Integration of multiwavelength lasers with fast electro-optical modulators,” Ph.D. thesis, TU Eindhoven (2004).
  14. B. Saleh and M. Teich, Fundamentals of Photonics (Wiley, 2007), Chap. 2.
  15. M. Smit and C. Van Dam, “PHASAR-based WDM-devices: principles, design and applications,” IEEE J. Sel. Top. Quantum Electron. 2, 236–250 (1996). [CrossRef]
  16. G. Eisenstein, “Semiconductor Optical Amplifiers,” IEEE Circuits Devices Mag. 5, 25–30 (1989). [CrossRef]
  17. P. Munñoz, R. Garcia-Olcina, J. D. Domenech, M. Rius, J. Capmany, L. R. Chen, C. Habib, X. J. M. Leijtens, T. de Vries, M. R. Heck, L. M. Augustin, R. Nötzel, and D. J. Robbins, “Multi-wavelength lasers based on an arrayed waveguide grating and Sagnac loop reflectors monolithically integrated on InP,” in Proceedings of the 15th European Conference on Integrated Optics (ECIO, 2010), pp. WeF2–1/2.
  18. P. Munoz, D. Pastor, and J. Capmany, “Modeling and design of arrayed waveguide gratings,” J. Lightwave Technol. 20, 661–674 (2002). [CrossRef]
  19. L. Soldano and E. Pennings, “Optical multi-mode interference devices based on self-imaging: principles and applications,” J. Lightwave Technol. 13, 615–627 (1995). [CrossRef]
  20. Y. Barbarin, E. Bente, T. de Vries, J. den Besten, P. van Veldhoven, M. Sander-Jochem, E. Smalbrugge, F. van Otten, E. Geluk, M. Heck, X. Leijtens, J. van der Tol, F. Karouta, Y. Oei, R. Notzel, and M. Smit, “Butt-joint interfaces in InP/InGaAsP waveguides with very low reflectivity and low loss,” in Proc. Symposium IEEE/LEOS Benelux Chapter , (IEEE, 2005).
  21. C. E. Spurgeon, Ethernet: The Definitive Guide (O’Reilly & Associates, Inc., 2000).
  22. A. Zilkie, J. Meier, M. Mojahedi, P. Poole, P. Barrios, D. Poitras, T. Rotter, C. Yang, A. Stintz, K. Malloy, P. Smith, and J. Aitchison, “Carrier dynamics of quantum-dot, quantum-dash, and quantum-well semiconductor optical amplifiers operating at 1.55 μm,” IEEE J. Quantum Electron. 43, 982–991 (2007). [CrossRef]
  23. F. Soares, F. Karouta, E. Geluk, J. Zantvoort, H. de Waardt, R. Baets, and M. Smit, “Low-loss InP-based spot-size converter based on a vertical taper,” in Proceedings of the 15th European Conference on Integrated Optics (ECIO, 2005), pp. 104–107.
  24. R. Garcia-Olcina, “Sistema de fabricacion de altas prestaciones de redes de difraccion de Bragg en fibra y aplicaciones al campo de los sensores opticos y a los sistemas de comunicaciones opticas,” Ph.D. thesis, Universitat Politecnica Valencia (2008).

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