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Wavelength-transparent nonlinear optical gate based on self-seeded gain modulation in folded tandem-SOA
Optics Express, Vol. 15, Issue 8, pp. 4929-4934 (2007)
http://dx.doi.org/10.1364/OE.15.004929
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– Abstract
1. Introduction
2. Principles
3. Static Domain Analysis: Extinction Ratio
4. Time Domain Analysis: 2R Regeneration, NOR gate
5. Conclusion
– References and links
– Abstract
1. Introduction
2. Principles
3. Static Domain Analysis: Extinction Ratio
4. Time Domain Analysis: 2R Regeneration, NOR gate
5. Conclusion
– References and links
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Abstract
In this paper, an all-optical nonlinear gate employing a folded tandem-SOA structure is proposed. With a partial reflection mirror for the amplified signal, we achieve a self-seeded gain modulation effect in the folded tandem-SOA, thus eliminating an external saturating source required for the conventional tandem-SOA optical gate. The performance analysis of the proposed device as a 2R regenerator / logic gates (NOR) shows excellent compatibility with the conventional structure, but in a highly integrated form with added benefit of wavelength transparency over wide spectral bandwidth (>100nm). Studies also have been carried out to investigate optimum operation condition of the device as a function of input wavelength and signal input power.
© 2007 Optical Society of America
1. Introduction
Non-linear optical devices, one of the promising network elements for future
all-optical 2R regenerated transmission systems and optical signal processing, have
been investigated in depth under various configurations in the past [1–5]. For such functionality, the high non-linearity
of Semiconductor Optical Amplifiers (SOA) is of perfect match, and has been widely
exploited under various architectures. In particular, SOAs utilizing gain
modulation, with its insensitivity to phase and simplicity for the device
implementation, have been successfully utilized to realize wavelength conversion [6, 7] or all optical logic gates [3, 4, 8, 9]. The most recent, and significant development in this
category includes the cascaded tandem-SOA structures [5, 9, 10], which provide much sharper nonlinear response curves than
single SOA based devices. Optical NOR-gate with Extinction Ratio (ER) enhancement
has been demonstrated using cascaded SOAs [9]. Utilizing also similar principles, ER enhancement and noise
compression of the signal was also successfully achieved [5, 10].
A.D. Ellis, A.E. Kelly, D. Nesset, D. Pitcher, D.G. Moodie, and R. Kashyap, “Error free 100Gbit/s wavelength conversion using grating assisted cross-gain modulation in 2mm long semiconductor amplifier,” Electron Lett. 34, 1958–1959 (1998) [CrossRef]
T. Durhuus, B. Mikkelsen, C. Joergensen, S. L. Danielsen, and K. E. Stubkjaer, “All-optical wavelength conversion by semiconductor optical amplifiers,” IEEE J. Lightwave Technol., 14, 942–954 (1996) [CrossRef]
A. Hamie, A. Sharaiha, and M. Guegan, “Demonstration of an all-optical logic OR gate using gain saturation in an SOA,” Micorwave Opt. Technol. Lett. 39, 39–42 (2003) [CrossRef]
S.H. Kim, J.H. Kim, B.G. Yu, Y.T. Byun, Y.M. Jeon, S. Lee, and D.H. Woo, “All-optical NAND gate using cross-gain modulation in semiconductor optical amplifiers,” Electron. Lett. 41, 1027–1028 (2005) [CrossRef]
X. Zhang, Y. Wang, J. Sun, D. Liu, and D. Huang, “All-optical AND gate at 10 Gbit/s based on cascaded single-port-coupled SOAs,” Opt.Express , 12, 361–366 (2004) [CrossRef] [PubMed]
A. Hamié, A. Sharaiha, M. Guégan, and B. Pucel, “All-optical logic NOR gate using two-cascaded semiconductor optical amplifiers,” IEEE Photonics Technol. Lett. 14, 1439–1441(2002) [CrossRef]
A. Hamié, A. Sharaiha, M. Guégan, and B. Pucel, “All-optical logic NOR gate using two-cascaded semiconductor optical amplifiers,” IEEE Photonics Technol. Lett. 14, 1439–1441(2002) [CrossRef]
A. Hamié, A. Sharaiha, M. Guégan, and B. Pucel, “All-optical logic NOR gate using two-cascaded semiconductor optical amplifiers,” IEEE Photonics Technol. Lett. 14, 1439–1441(2002) [CrossRef]
In this paper, we propose a novel all optical gate structure, which utilizes
self-seeded gain modulation effects in folded tandem-SOA. Instead of the
conventional tandem-SOA approach, which uses an extra external continuous wave (CW)
source for the generation of the XGM (Cross gain modulation) effect, we use a
self-seeded, gain modulation effect of the signal, by employing a partial reflection
mirror at the output. Comparison of suggested structure with the CW-assisted
tandem-SOA optical gate shows that compatible performance factors can be achieved
with much simpler device structure, enabling higher level of integration of the
device at a reduced cost; also with the added critical benefit of wavelength
transparency in the signal regeneration. Investigations on the optimum operating
conditions of the device, as a function of input signal wavelength
(>100nm) and input power have been carried out.
2. Principles
Fig. 1. Schematics of CW-assisted tandem-SOA optical gate (case A) schematics of
folded tandem-SOA optical gate (case B)
Figure 1 illustrates the basic concept of;
A) the CW-assisted tandem-SOA all-optical gate [9], and B) the folded tandem-SOA all-optical
gate - proposed in this paper. Serially connected two SOAs (SOA1, SOA2 of gain
G1
, G2
) takes input
signal Pin
at the input port of SOA1 as well as
saturating signal at the output port of SOA2 (for the case A, from
external CW source; for the case B, it is amplified and reflected
input signal rG1G2Pin
, where
r is a mirror reflectance). Stating the operation principle for
CW-assisted tandem SOA structure (case A); CW saturating tone
counter-propagating the SOA2 experiences XGM effects from the input signal
G1Pin
, and provides inverted
patterns of P∼in
at the
mid-stage output port (Po2
). Meanwhile, at this stage,
same magnitude of Po2
(∝
P∼in
) at the same time entering the
first stage SOA1 also interacts with Pin
through the XGM
effect, resulting further enhancement in the extinction ratio of the signal at the
output port of the SOA1 (Po1
∼
G1Pin
). Note that these resulting
highly non-linear transfer characteristics (e.g., between
Pin
and Po1
,
Pin
and Po2
) of
tandem SOA structures can be effectively utilized to achieve all-optical
regeneration [5, 10] or all-optical NOR gate [9].
A. Hamié, A. Sharaiha, M. Guégan, and B. Pucel, “All-optical logic NOR gate using two-cascaded semiconductor optical amplifiers,” IEEE Photonics Technol. Lett. 14, 1439–1441(2002) [CrossRef]
A. Hamié, A. Sharaiha, M. Guégan, and B. Pucel, “All-optical logic NOR gate using two-cascaded semiconductor optical amplifiers,” IEEE Photonics Technol. Lett. 14, 1439–1441(2002) [CrossRef]
Now understanding that; 1) usually the flight time of the signal can be neglected in
the reasonable device operation speed, and that 2) the signal power
at the output port of SOA2 is highly saturated (almost constant, irrespectively of
the symbol type or delay of Pin
), it is meaningful to
consider the reflected output power of SOA2 as an alternative of external CW source,
to similarly obtain the nonlinear transfer function which was observed in the case
A). Case B) of Fig. 1 shows such a folded tandem SOA structure, which
utilizes a self-seeded gain modulation effect between the signal and
counter-propagating, amplified reflected signal.
3. Static Domain Analysis: Extinction Ratio
To begin, the performance of the folded tandem-SOA optical gate was analyzed in the
static domain, considering both forward / backward propagating signals (both at
1549.2nm). At the output port of SOA2, a mirror of reflectance r
(r = Pr
/Pi
) was assumed. Fast and highly accurate analysis was
made utilizing the integral equation formalism of SOA [11]. For the parameters of SOA1 (SOA2), device length of
250μm, current of 500mA, confinement factor of 0.4, material gain
coefficient of 2.7e×1016cm2, refractive index of
3.7, and material scattering loss of 34cm-1 were used.
Y. J. Jung, P. Kim, J. Park, and N. Park, “Integral equation approach for the analysis of high-power semiconductor optical amplifiers,” Opt. Express 14, 2398–2403 (2006) [CrossRef] [PubMed]
In Fig. 2, we present the signal power distribution curves in
folded tandem-SOA for different input power levels (Pin
= -6dBm, -2dBm, and 2dBm, labeled as ‘A’,
‘B’, and ‘C’ in the Fig.
r = 0.5%). The output power Po1
measured at the signal extraction point (3dB-coupler in the middle, see Fig. 1 and 2) were -1.9dBm, 6.8dBm and 16.9dBm, with corresponding gain
values (G1
) of 4.1dB, 8.8dB and 14.9dB respectively. As
shown, the mid-stage gain G1
of tandem-SOA measured at
the output of SOA1 increased with the input signal strength, with its highly
nonlinear saturation behavior - thus providing the enhancement in the signal
extinction ratio. In terms of static extinction ratio, as much as 10.8dB of net ER
gain was achieved with 8dB of input ER (-6 ∼ 2dBm) and 18.8dB of output
ER (-1.9 ∼ 16.9dBm).
Fig. 2. Power distributions in the folded tandem-SOA, at different input signal
(-6dBm, -2dBm, and 2dBm). Note that, the injected input signal propagates
from right to left, and the output signal is extracted by a 3dB-coupler
located in the middle. At the end of SOA2 (z=0), the amplified signal is
reflected from the mirror (starting from -5 ∼ 0dBm range in the
Fig.)
Important to note is that the reflected power at the SOA2 output point was almost
identical (∆P ∼ 1dB) from the saturated
operation of tandem-SOA, irrespective of the input signal strength (∆P =
8dB); thus virtually acting as a continuous wave source irrespectively of the symbol
type or delay of Pin
. Further, in this regard, with the
adjustment of the mirror reflectance, it was also possible to change the optimum
operation point of the device (equivalent to the CW power adjustment in [5, 10]). In Fig. 3, we plot the output power
Po1
from the SOA1, as a function of input signal power
Pin at different mirror reflectivity (r = 4%, 2%, 0.5% and0.1%).
The obtained optimum input power Pin
for the maximum ER
enhancement was 7dBm with 4%, 4dBm with 2%, -1.7dBm with r = 0.5%,
and -8.5dBm with r = 0.1%, respectively. Finer adjustment of
optimum input power for ER enhancement should be possible with the change in mirror
reflectance, or with the tunable MEMS mirror.
As mentioned earlier, one of the critical / inherent benefit of the proposed device
lies in the wavelength transparency during the process of signal regeneration,
without the need of external sources or wavelength tuning of it. In order to find
out the operating bandwidth of the device, input signals at different wavelength
(1450nm, 1500nm, 1550nm, all with -1.7dBm) have been tested. As can be seen in Fig. 4, almost identical numbers in ER enhancement was
observed for all the signal wavelength, well exceeding 100nm, with the corresponding
optimum mirror reflectivity (0.5%, 0.7%, 1.6% for 1550, 1500, 1450nm signal,
covering from the gain peak wavelength to half-maximum gain wavelength).
4. Time Domain Analysis: 2R Regeneration, NOR gate
For the transient analysis of tandem-SOA, we plot in Fig 5 traces of Pin
,
Po1
and Po2
,
calculated with the transfer matrix method [12, 13] (r = 0.5%, and CW tone = -1.7dBm).
M. G. Davis and R. F. O’Dowd, “A transfer matrix method based large-signal dynamic model for multielectrode DFB lasers,” IEEE J. Quantum Electron. 30, 2458–2466 (1994) [CrossRef]
H. Lee, H. Yoon, Y. Kim, and J. Jeong, “Theoretical study of frequency chirping and extinction ratio of wavelength-converted optical signals by XGM and XPM using SOA’s,” IEEE J. Quantum Electron. 35, 1213–1219 (1999) [CrossRef]
In contrast to the case of CW-assisted tandem SOA, the slight reduction in the SOA2
output power (Po2
), and signature of mirror reflection
(or delay of the signal pattern) at the rising / falling edges of the pulse were
observed. For the output of SOA1 (Po1
), about 19dB of
dynamic ER (-2dBm to 17dBm) was achieved, consistent with the number from static
analysis.
To further investigate the impact of ER enhancement from the system perspective (as a
2R regenerator), the Q factor of the input / output signal of the device was also
compared. 10Gbps, 127 bit super-Gaussian PRBS input signal was used. Also assumed
was ASE noise of -13.64dBm/0.1nm, with an OSNR of 14.64dB for 1dBm of average signal
input power. Before the receiver, a 2nd order Butterworth optical filter of 90GHz
3dB bandwidth, and a 2nd order Butterworth electrical filter of 7.5GHz bandwidth
were used. Assuming 10% of timing jitter from the decision circuitry, calculated
Q-factors before / after the regeneration were 4.06 and 7.01, respectively.
Significant improvement in Q value over 3 (or in terms of BER, 9 orders of
improvement) was achieved from the 2R operation of the device. Worth to note, the
mirrored spike effect in Fig. 5 (as a signature of signal delay in the device,
combined with the reflections from mirror or facets) were filtered out after the
receiver electrical filter, not seriously affecting the overall Q factor values.
Fig. 5. Transient responses of; CW-assisted tandem SOA (solid) and folded tandem SOA
(dash). Pin
magnified by 10 times
Fig. 6. Eye-diagram of 10Gbps signal, before (a) and after (b, c, d with
Pin
= -1, 1.5, 4dBm) the 2R
regeneration. Q
in
= 6)
For the 2R operation detailing the eye-opening / Q-factor changes on the input signal
power variations, eye-diagrams and Q-factors before / after the 2R regeneration are
illustrated in Fig. 6 and 7 respectively. As can be seen in Fig. 6 (c), a well-defined, wide eye was obtained after the
2R regeneration at the optimum input power. As expected, increased level of noise
was introduced from the ‘1’ level (Fig. 6b) or ‘0’ level (Fig. 6d) when the input bias was off-optimal point. Depending
on the input Q-factor (Q
in
= 4, 5, 6), Q factor improvement of 3 ∼ 6, for 1 ∼ 3dB
input signal strength window were obtained (Fig. 7).
Finally, the device functionality as a NOR gate was investigated. In Fig. 8, we plot the SOA2 output
Po2
against two input signals
(PA
in
,
PB
in
), which were simultaneously coupled
to the SOA1 input port. As shown, the perfect operation of NOR function was
obtained, with a negligible amount of amplitude variation and time delay (associated
with SOA gain recovery time, especially in the rising edge of the pulse. Similar
tendency can be found in Fig. 5).
5. Conclusion
Exploiting the highly saturated nature of tandem-SOA gain, in this paper we proposed
and also demonstrated that a self-seeded gain modulation effect can be created, with
the simple addition of low-reflectivity mirror; constituting a much simpler
structure of folded tandem-SOA all-optical logic gate with inherent wavelength
transparency. Performance compatibility of the device with the prior arts has been
demonstrated in terms of various functionality, such as 2R regenerator and NOR gate.
With the highly integrated structure and reduced cost, without the introduction of
external saturating tone and added transparency in wavelength, the proposed
structure should benefit the realization of the all optical gate, such as a
nonlinear optical gate for 2R regeneration and NOR gate in the all-optical,
wavelength routed network.
References and links
J.C. Simon, “All optical regeneration,” ECOC , 469–467 (1998) | |
O. Leclerc, B. Lavigne, E. Balmefrezol, P. Brindel, L. Pierre, D. Rouvillain, and F. Seguineau, “Optical Regeneration at 40 Gb/s and Beyond,” IEEE J. Lightwave Technol . 21, 2779–2790 (2003) [CrossRef] | |
A. Hamie, A. Sharaiha, and M. Guegan, “Demonstration of an all-optical logic OR gate using gain saturation in an SOA,” Micorwave Opt. Technol. Lett. 39, 39–42 (2003) [CrossRef] | |
S.H. Kim, J.H. Kim, B.G. Yu, Y.T. Byun, Y.M. Jeon, S. Lee, and D.H. Woo, “All-optical NAND gate using cross-gain modulation in semiconductor optical amplifiers,” Electron. Lett. 41, 1027–1028 (2005) [CrossRef] | |
G. Contestabile, R. Proietti, N. Calabretta, L. Giorgi, and E. Ciaramella, “Evidence of noise compression by cross gain compression in SOAs,” OFC, JThB29 (2006) | |
A.D. Ellis, A.E. Kelly, D. Nesset, D. Pitcher, D.G. Moodie, and R. Kashyap, “Error free 100Gbit/s wavelength conversion using grating assisted cross-gain modulation in 2mm long semiconductor amplifier,” Electron Lett. 34, 1958–1959 (1998) [CrossRef] | |
T. Durhuus, B. Mikkelsen, C. Joergensen, S. L. Danielsen, and K. E. Stubkjaer, “All-optical wavelength conversion by semiconductor optical amplifiers,” IEEE J. Lightwave Technol., 14, 942–954 (1996) [CrossRef] | |
X. Zhang, Y. Wang, J. Sun, D. Liu, and D. Huang, “All-optical AND gate at 10 Gbit/s based on cascaded single-port-coupled SOAs,” Opt.Express , 12, 361–366 (2004) [CrossRef] [PubMed] | |
A. Hamié, A. Sharaiha, M. Guégan, and B. Pucel, “All-optical logic NOR gate using two-cascaded semiconductor optical amplifiers,” IEEE Photonics Technol. Lett. 14, 1439–1441(2002) [CrossRef] | |
G. Contestabile, R. Proietti, N. Calabretta, and E. Ciaramella, “All optical regeneration by cross gain compression in semiconductor amplifiers,” ECOC, 3, 415–416 (2005) | |
Y. J. Jung, P. Kim, J. Park, and N. Park, “Integral equation approach for the analysis of high-power semiconductor optical amplifiers,” Opt. Express 14, 2398–2403 (2006) [CrossRef] [PubMed] | |
M. G. Davis and R. F. O’Dowd, “A transfer matrix method based large-signal dynamic model for multielectrode DFB lasers,” IEEE J. Quantum Electron. 30, 2458–2466 (1994) [CrossRef] | |
H. Lee, H. Yoon, Y. Kim, and J. Jeong, “Theoretical study of frequency chirping and extinction ratio of wavelength-converted optical signals by XGM and XPM using SOA’s,” IEEE J. Quantum Electron. 35, 1213–1219 (1999) [CrossRef] |
OCIS Codes
(130.3750) Integrated optics : Optical logic devices
(200.3760) Optics in computing : Logic-based optical processing
(200.4660) Optics in computing : Optical logic
(250.5980) Optoelectronics : Semiconductor optical amplifiers
ToC Category:
Integrated Optics
History
Original Manuscript: December 19, 2006
Revised Manuscript: April 5, 2007
Manuscript Accepted: April 5, 2007
Published: April 9, 2007
Citation
Young Jin Jung, Jonghan Park, and Namkyoo Park, "Wavelength-transparent nonlinear optical gate based on self-seeded gain modulation in folded tandem-SOA," Opt. Express 15, 4929-4934 (2007)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-8-4929
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References
- J.C. Simon, "All optical regeneration," ECOC, 469-467 (1998)
- O. Leclerc, B. Lavigne, E. Balmefrezol, P. Brindel, L. Pierre, D. Rouvillain, and F. Seguineau, "Optical Regeneration at 40 Gb/s and Beyond," IEEE J. Lightwave Technol. 21, 2779-2790 (2003) [CrossRef]
- A. Hamie, A. Sharaiha, M. Guegan, "Demonstration of an all-optical logic OR gate using gain saturation in an SOA," Micorwave Opt. Technol. Lett. 39, 39-42 (2003) [CrossRef]
- S.H. Kim, J.H. Kim, B.G. Yu, Y.T. Byun, Y.M. Jeon, S. Lee, D.H. Woo, "All-optical NAND gate using cross-gain modulation in semiconductor optical amplifiers," Electron. Lett. 41, 1027-1028 (2005) [CrossRef]
- G. Contestabile, R. Proietti, N. Calabretta, L. Giorgi and E. Ciaramella, "Evidence of noise compression by cross gain compression in SOAs," OFC, JThB29 (2006)
- A.D. Ellis, A.E. Kelly, D. Nesset, D. Pitcher, D.G. Moodie and R. Kashyap, "Error free 100Gbit/s wavelength conversion using grating assisted cross-gain modulation in 2mm long semiconductor amplifier," Electron Lett. 34, 1958-1959 (1998) [CrossRef]
- T. Durhuus, B. Mikkelsen, C. Joergensen, S. L. Danielsen, and K. E. Stubkjaer, "All-optical wavelength conversion by semiconductor optical amplifiers," IEEE J. Lightwave Technol., 14, 942-954 (1996) [CrossRef]
- X. Zhang, Y. Wang, J. Sun, D. Liu, D. Huang, "All-optical AND gate at 10 Gbit/s based on cascaded single-port-coupled SOAs," Opt.Express, 12,361-366 (2004) [CrossRef] [PubMed]
- A. Hamié, A. Sharaiha, M. Guégan, and B. Pucel, "All-optical logic NOR gate using two-cascaded semiconductor optical amplifiers," IEEE Photonics Technol. Lett. 14, 1439-1441(2002) [CrossRef]
- G. Contestabile, R. Proietti, N. Calabretta, E. Ciaramella, "All optical regeneration by cross gain compression in semiconductor amplifiers," ECOC, 3, 415-416 (2005)
- Y. J. Jung, P. Kim, J. Park, N. Park, "Integral equation approach for the analysis of high-power semiconductor optical amplifiers," Opt. Express 14, 2398-2403 (2006) [CrossRef] [PubMed]
- M. G. Davis and R. F. O’Dowd, "A transfer matrix method based large-signal dynamic model for multielectrode DFB lasers," IEEE J. Quantum Electron. 30, 2458-2466 (1994) [CrossRef]
- H. Lee, H. Yoon, Y. Kim, and J. Jeong, "Theoretical study of frequency chirping and extinction ratio of wavelength-converted optical signals by XGM and XPM using SOA’s," IEEE J. Quantum Electron. 35, 1213-1219 (1999) [CrossRef]
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