00996589

8/13/2019 00996589

1/7

682 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 20, NO. 4, APRIL 2002

Performance Analysis on Semiconductor LaserAmplifier Loop Mirrors

Hanxing Shi, Member, IEEE

AbstractOperating characteristics of the semiconductor laseramplifier loop mirror (SLALOM) in optical time-division multi-plexing (OTDM) applications are investigated in theory. The injec-tion current of the semiconductor laser amplifier (SLA) should beadjusted to realize a flat and high switching window. The channelcrosstalk induced by thefinite carrier lifetimeand thesignal timing

jitter should be balanced. The optimal switching window widthshould be slightly wider than half of the OTDM signal bit interval.The control pulse should be narrower than one-third of the OTDMbit interval in order not to deteriorate the bit error rate (BER)performance. Further discussion indicates that the nonlinear gaincompression in the SLA becomes a crucial limit for the SLA-basedall-optical switches to be used in the terahertz applications.

Index TermsDemultiplexing, fiber optical communications,nonlinear gain compression, semiconductor laser amplifier (SLA).

I. INTRODUCTION

ALL-OPTICAL switching is essential for high-speed op-tical time division multiplexing (OTDM) systems and net-works. A semiconductor laser amplifier loop mirror (SLALOM)

based on the optical nonlinearity of a semiconductor laser am-

plifier (SLA), which is also called the terahertz optical asym-

metric demultiplexer (TOAD), is one of the most promising can-

didates [1][4]. With an interferometric construction, it is based

on a nonlinear phase shift induced by a change in carrier den-

sity in the SLA, but the switching speed is not restricted by thecarrier recovery rate.

The other fiber-based optical switches, such as soliton gates

[5] and nonlinearoptical loop mirror (NOLM)[6], [7], require at

least tens of meters of fiber, high control pulse energy, and strict

wavelength matching between signal and control pulses. They

are also sensitive to both polarization and environment. Elec-

troabsorption modulator (EAM) switches, as electrically con-

trolled switching, are also widely studied [8], [9]. However, they

induce large optical loss and need the device to have a steep

nonlinear absorption curve to realize a picosecond switching

window.

SLA-based all-optical switches offer the advantages of signal

amplification, wavelength flexibility, low control pulse energy,

and large dynamic range. They can also be polarization insensi-

tive. Based on a similar mechanism as the SLALOM, other in-

terferometric arrangements, such as MachZehnder interferom-

Manuscript received December 4, 2000; revised August 15, 2001. This workwas supported in part by Beijing University of Posts and Telecommunicationsthrough National 863 Project.

The author was with the Department of ECE, University of California, SantaBarbara, Santa Barbara, CA 93106 USA. She is now with Yotta Networks, Inc.,Plano, TX 75074 USA.

Publisher Item Identifier S 0733-8724(02)03335-2.

eters (MZIs) or Michelson interferometers (MIs), provide addi-

tional flexibility and monolithic integration for stable operation

[10][12]. So far, 250-Gb/s demultiplexing has been demon-

strated with a SLALOM having 4-ps switching window [2].

Therefore, SLA-based all-optical switches have a bright per-

spective in practical applications.

Although SLA switches have been extensively studied in

experiments, their operating performances have not been thor-

oughly investigated in theory. The switching characteristics,

which are governed by many factors, such as SLAs position

in the loop, SLAs gain dynamics, and shape and power of

the control pulse, make the analysis complex. In [13], Zhouetal. analyzed the degradation of the signal quality induced by

the uneven optical coupler and the spontaneous emission in

the SLA, but they ignored several crucial issues related to the

light pulses and the switch window configuration. In this paper,

we will investigate these issues from the point of view of the

system performance, especially the configurations of the SLA,

the effect of the inevitable timing jitter in the received signal

pulses, the optimization of the switching window width, and

the requirement on control pulsewidth.

In addition, Tang et al. proposed, in theory, that if a pi-

cosecond control pulse is used, a fast gain depletion process

will appear in the dynamics of SLA and further distort the

switching window [14]. However, how greatly does thedistorted switching window affect the demultiplexing perfor-

mance? In this paper, we will investigate the influence of fast

gain depletion on the bit error rate (BER) performance of the

demultiplexed signal and confirm the upper limitation to the

operating speed of SLA switches.

The remainder of the paper is organized as follows. Section II

introduces the operating principle of the SLALOM and estasb-

lishes the theoretical model. In Section III, the demultiplexing

performance of the SLALOM is systematically analyzed, es-

pecially focusing on four issues: 1) the design of the SLA; 2)

the influence of the signal timing jitter; 3) the optimization of

the switching window width; and 4) the limitation to the con-

trol pulsewidth. In Section IV, the influence of nonlinear gaincompression on the BER performance and the induced speed

limitation of SLA switches are analyzed.

II. THEORETICALMODEL

Fig. 1 shows the schematic diagram of the SLALOM

device with the Sagnac interferometric configuration [1]. An

SLA is located asymmetrically inside the fiber loop as the

nonlinear medium. Its offset distance (where

is the velocity of light in the fiber) from the loop midpoint

0733-8724/02$17.00 2002 IEEE
http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-

8/13/2019 00996589

2/7

SHI: PERFORMANCE ANALYSIS ON SLALOM 683

Fig. 1. Schematic diagram of the SLALOM device. PC: polarizationcontroller. EDFA: Erbium-doped fiber amplifier. DSF: dispersion-shifted fiber.

approximately determines the switching window width of

the SLALOM. The received OTDM signal with a multiplexing

bit rate of (where is the channel number

of the OTDM system and is the single-channel bit rate)

is launched into port A and split into two counterpropagating

signals with equal amplitudes and identical phases. The optical

power of the OTDM signal is chosen small enough that it does

not significantly affect the dynamics of the SLA. On the otherhand, intense control pulses with single-channel repetition

rate are transmitted into the fiber loop via a wavelength

division multiplexing (WDM) coupler in order to change the

dynamics of SLA. In the absence of this control pulse, the

whole configuration operates as a symmetric loop and the

recombined signal after the loop is completely reflected back

from the port A. However, things will be physically different

when the refractive index in the SLA is greatly changed by the

existence of strong control pulse. Due to SLAs offset from the

loop midpoint, the two counterpropagating signals will arrive at

the SLA with predicted time delay in order to experience the

different dynamic states of the SLA. As a result, the two signals

will experience different gains and different phase shifts. After

they are recombined through the coupler, the corresponding

target channel will be transmitted out from port B of the loop,

and the other channels will be reflected back from port

A.

The dynamic response of SLA taking into account the intra-

band effects can be described as [14]

(1a)

(1b)

(1c)

where and are t he o ptical p ower a nd t he p hase o f

the input light, respectively, is the SLAs dynamic gain,

is the small signal gain, is the mode

confinement factor, is the differential gain coefficient, is

thetransparentcarrier density, is thetransparentinjection cur-

rent, is the saturation energy, is the spontaneous carrier

lifetime, is the internal loss, is the linewidth enhancement

factor, and is the nonlinear gain compression factor, which is

mainly related to intraband processes, such as carrier heating,

spectral hole burning, and two-photon absorption.

According to the Sagnac interferometric configuration, the

optical power of the demultiplexed signal output from port B

of the SLALOM is [13]

(2)

where is the optical power of the received OTDM signal,

is the splitting ratio of the fiber coupler, and are the

dynamic gain experienced in the clockwise and counterclock-

wise signal pulses, respectively, is their gain

ratio, and is the phase differ-

ence between the two signal pulses. When no control pulse ex-

ists in a symmetric loop, i.e., and , no signal is

transmitted out from port B. On the other hand, when ,

the power of the signal pulse emitted from port B can be max-

imized.

In practical OTDM applications, both timing jitter and

temporal deviation between signal and control pulses inevitably

exist, especially after long-distance transmission. At the re-ceiving port, they will be converted into intensity fluctuations

of the demultiplexed signal and deteriorate the system perfor-

mance [15]. In a previous work [16], we have established a

comprehensive theoretical model for the timing jitter of signal

pulses in all-optical demultiplexers and analyzed its influence

on fiber-based Sagnac interferometric switches, i.e., NOLMs.

In this paper, the same timing jitter model, in conjunction with

a conventional optically preamplified receiver model [17], is

adopted to numerically analyze the SLALOMs demultiplexing

performance.

It is assumed that the temporal relationship between signal

and control pulses satisfies a Gaussian probability distribution

as follows [16]:

(3)

where is the shift of the received signal pulse corresponding to

the control pulse, the mean is the synchronization deviation

of signal pulses, and is the root mean square (rms) of the

timing jitter of signal pulses.

In addition to the general noise terms in the optical receiver

[17], the additional noise induced by the amplified spontaneous

emission (ASE) in the SLA should also be considered. In gen-

eral, the equivalent photocurrent of ASE power in the SLA isexpressed as [18]

(4)

where is the spontaneous emission factor, is the electronic

charge, and is the bandwidth of the optical filter. Thus, the

additional noise terms induced by the SLA are mainly the ASE

shot noise and the signal-spontaneous beat noise [18]

(5)

(6)
http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-

8/13/2019 00996589

3/7


TABLE ICOMMON PARAMETER VALUES USED IN

THECALCULATIONS

where is the conversion efficiency of the optical receiver,

is its electrical bandwidth, and is the equivalent photocurrent

of the amplifier input power. Considering all of the noise terms,

the BER of the demultiplexed signal is given by [ 17]

BER erfc (7)

where erfc is the error function, and are

the average optical powers of 1 and 0 code of the demulti-

plexed signal in the whole frame, respectively, and and

are their intensity noises, respectively.

In the next section, we study the case of a 10 10 Gb/s

OTDM system to investigate SLALOMs demultiplexing

performance. For comparison, we also cite the performance

of 4 10, 16 10, and 4 40 Gb/s systems. The default

parameters used in the calculations are summarized in Tables I

and II. The reader is referred to [16] for the parameters of the

optical receiver.

III. PERFORMANCEANALYSIS

In this section, we investigate the performance of the

SLALOM for applications slower than 200 Gb/s. Considering

that intraband processes become noticeable for control pulses

narrower than 1 ps only [14], nonlinear gain compression is

temporarily neglected in this section and will not affect the

conclusions.

A. SLA Configurations

It is clear, from (2), that both the power and shape of the de-

multiplexed signal pulses depend on the gain ratio of the two

TABLE IIDIFFERENTPARAMETERVALUES FORDIFFERENTBITRATESYSTEMS

Fig. 2. Dependence of the normalized demultipelxed signal power on the gain ratio of two signal branches , splitting ratio offiber coupler , and SOA linewidth enhancement factor .

counterpropagating signals through the SLA. Therefore, opti-

mizing the SLAs parameters is the first step to obtain the best

demultiplexing performance.

Fig. 2 illustrates the dependence of the normalized demul-

tiplexed signal power on the gain ratio of two counterpropa-

gating signals, splitting ratio of the fiber coupler and theSLAslinewidth enhancement factor . As a Sagnac interferometer,

the symmetry of the optical coupler is a requisite to avoid the

intrinsic crosstalk [15]. For simplification, an ideal 1:1 optical

coupler is assumed in the following. It is also shown, in Fig. 2,

that the normalized demultiplexed signal can be maximized with

thegain ratio between 0.2 and 0.4. However, the optimal value

of varies with the linewidth enhancement factor . An SLA

with a larger requires a larger gain ratio but also produces a

higher normalized output power. Therefore, an SLA with high

linewidth enhancement factor can improve the demultiplexing

performance, which was experimentally verified by Manning

[19].

Fig. 3 shows the dynamic gains of two signal pulses, and, and the corresponding switching window of a SLALOM

under different injection current in the 10 10 Gb/s OTDM

system. The width of the switching window is approximately

equal to the time difference when the two counterpropagating

signal pulses separately arrive at the SLA, which is twice the

temporal offset of SLA from the fiber loop center [1]. The lower

subfigure indicates that there is an optimal injection current to

realize a high and flat switching window. Insufficient injec-

tion current reduces the signal gain and further degrades the

switching window amplitude. Conversely, an overbiased SLA

will generate a gain ratio and a phase difference greater than

the optimal values, which results in a dented switching window.
http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-

8/13/2019 00996589

4/7


Fig. 3. Dynamic gains obtained by two signal branches (upper) and thecorresponding switch window of SLALOMs (lower) in a 4 2 10 Gb/s system.

Therefore, the injection current of the SLA must be specificallyadjusted according to the control pulse power.

B. Optimizations of Switching Window Width and Temporal

Parameters of Signal Pulses

The switching window width of the SLALOM is determined

by the position deviation of the SLA in the fiber loop. As shown

in Fig. 3, there is a switching floor outside the main switching

window, which means that even for the nontarget channels,

signal leakage from port B is still inevitable. It originates from

the finite carrier lifetime in the SLA, which results in finite

recovery time of the dynamic gain and, finally, produces a gain

discrepancy between the two signal pulses outside the mainwindow. This is the main contribution to the channel crosstalk

in SLALOM operation. Widening the switching window can

increase the gain difference outside the switching window and

aggravate the channel crosstalk.

However, in practice, the narrowest switching window does

not correspond to the best system performance. If the switching

window is too narrow, the unavoidable timing jitter in the re-

ceived signal will be transformed into intensity noise in the de-

multiplexedsignal and increase the biterror rate. Hence, to trade

off the effects of the channel crosstalk and the signal timing

jitter, the switching window width of the SLALOM has to be

optimized to realize the best demultiplexing performance. Be-

sides the timing jitter, any deviation of the target signal pulsesfrom the window center will also increase the error rate. There-

fore, both the signal timing jitter and temporal deviation

between signal and control pulses should be controlled.

Fig. 4 shows the power penalty induced by both and

under different switching window widths in a 10 10 Gb/s

situation. The power penalty is defined as the excess signal

power required for the 10 BER value in comparison to the

ideal case having zero and optimized value of . The refer-

ence values of the signal power received by the receiver are, re-

spectively, 1.4 dBm, 2.9 dBm, and 2.7 dBm for , ,

and ps. It is clear that the optimal temporal deviation should

be slightly beyond half of the switching windowwidth , which

Fig. 4. Power penalty induced by signal timing jitter and temporal deviationbetween signal and control pulses in a 10 2 10 Gb/s situation.

means that the target signal pulse should be positioned around

the switching window center. The requirement of the small de-

viation beyond is because that the finite control pulsewidthretards the switching window. Any small departure from this

optimum will seriously deteriorate the demultiplexing perfor-

mance. Under the fixed , the timing jitter of the signal pulse

will increase the power penalty, especially if the signal pulse de-

viates from the switching window center. In addition, the wider

switching window can tolerate larger signal timing jitter for the

same power penalty. Comparing the received signal powers in

the three cases, we also find that there is an optimal switching

window width corresponding to the minimal signal power.

Considering all of these phenomena, Fig. 5 shows the depen-

dence of demultiplexing performance on the switching window

width and the pulse timing jitter for different bitrate cases. Thereceived signal powers are, respectively, 5.8, 2.9, 1.0, and

5.0 dBm for the 4 10, 10 10, 16 10, and 4 40 Gb/s sys-

tems. In Fig. 5(b), the horizontal axis corresponds to normal-

ized to the signal pulse interval in order

to compare the different bit-rate cases. The temporal deviation

between signal and control pulses are set as optimum, ac-

cording to this analysis. Under fixed timing jitter, there is an

optimal switching window width, which is a little bit wider than

half of the OTDM bit interval . This phenomenon was ex-

perimentally observed as the existence of an optimal switching

contrast while varying the switching window width [11]. In the

10 10 Gb/s case, the optimal value of is about 6 ps when

ps. With a worse timing jitter, a wider switching windowis required to tolerate the timing jitter and to obtain the optimal

BER performance. Besides, at higher speed, the SLALOM is

more sensitive to the signal timing jitter, which asks for stricter

requirement to the optimization of the switching window width.

Further comparing the curves of 16 10 and 4 40 Gb/s

cases, it is interesting to see that, in the system with fewer

channels, i.e., relatively higher single-channel bit rate , the

demultiplexing performance is more sensitive to the widening

of the switching window above . This is because, for

higher , there is less time for the SLA to recover its dynamic

gain between two successive control pulses in order to generate

worse crosstalk from the nontarget channels. Also, the system
http://-/?-http://-/?-

8/13/2019 00996589

5/7


Fig. 5. BERperformanceof demultiplexed signalversus switchwindow width

under different signal timing jitters

. (a) 102

10 Gb/s; (b) 42

10, 162

10,and 4 2 40 Gb/s.

with a higher single-channel bit rate requires higher optical

power of the received signal for the same BER value. Therefore,

in order to realize the specified OTDM speed, it is beneficial to

adopt a combination of a higher channel number and a slower

single-channel bit rate.

Fig. 5(a) also shows that in the 10 10 Gb/s system, the

jitter tolerance of a SLALOM with ps in the range of

10 BER is about 1.5 ps. Compared with a NOLM having

the same interferometric configuration [16], the SLALOM has

a relatively higher tolerance for timing jitter. In a fiber-based

NOLM switch, the switching window shape is determined bythe integral effect of the walkoff between signal and control

pulses along a few kilometers of fiber [6]. At any moment,

the instantaneous window of the nonlinear interaction has the

same shape as the control pulse and is very sensitive to the

pulse timing jitter. All of the fiber-nonlinearity-based switches

require this strict synchronization. However, the optical nonlin-

earity of a SLALOM is concentrated in the SLA element and

the switching window does not change with time. Therefore,

SLA-based switches are inherently less sensitive to the signal

timing jitter, which was proved experimentally by Sokoloff [3].

It is undoubtedly one of the critical benefits in practical appli-

cations.

Fig. 6. Dependence of demultiplexing performance on normalized controlpulsewidth in different OTDM cases.

C. Limitation on Control Pulsewidth

As shown previously, the temporal deviation of the SLA

from the fiber loop center, i.e., , determines the switching

window width. In addition, the form of the control pulse is also

important for determining the shape, especially the edges, of

the window. A narrower control pulse can generate a flatter

switching window, which has better tolerance for signal timing

jitter. A narrower pulse can also achieve sharper edges of

the switching window, which reduces the crosstalk from the

neighboring channels.

Fig. 6 shows the dependence of the BER performance on

the normalized control pulsewidth under different OTDM

bit rates. The horizontal axis is the ratio of the full-width at

half-maximum (FWHM) of the control pulse to the signal pulse

interval . Because the dynamic gain of the SLA is involvedwith the total optical energy, the control pulse energy is fixed for

different cases. The optimal switching windows are set as 13,

6, 4, and 4 ps for the 4 10, 10 10, 16 10, and 4 40 Gb/s

systems, respectively. The received signal powers are the same

as in Section III-B.

It is shown that there is some limit on the control pulsewidth

to guarantee the specified demultiplexing performance. The

upper limit of in the scale of 10 BER value is about 1/3 of

the single-channel bit interval. For example, in a 10 10 Gb/s

system, the control pulse should be narrower than 3 ps to obtain

BER .

IV. LIMITATION OFNONLINEARGAINCOMPRESSION

In the previous section, we only discussed the OTDM sys-

tems slower than 200 Gb/s. In terahertz OTDM applications,

there are mainly three factors limiting the resolution of the SLA

switches: 1) the length of the device; 2) the control pulsewidth;

and 3) the intraband processes. The finite length of the SLA de-

cides the propagation time of the pulses and further induces an

asymmetric switching window [3], [20]. Furthermore, the width

of the switching window cannot be narrower than the control

pulsewidth [21]. These limitations could be weakened by using

a shorter device and a narrower control pulse. However, with

a picosecond control pulse in a terahertz system, the intraband
http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-

8/13/2019 00996589

6/7


Fig. 7. Dynamic gain of SLA and the corresponding switch window shape ofSLALOM with in a 40 2 10 Gb/s OTDM situation.

Fig. 8. BER performance versus control pulsewidth in the 40 2 10 Gb/sOTDM system with and without consideration of nonlinear gain compression.

processes lead to nonlinear gain compression in SLA, which is

no longer negligible.

This section discusses this issue with an example of

40 10 Gb/s system. The related parameters are that the signal

pulsewidth is 0.6 ps, ps, ps, and the received

signal power is 2.9 dBm. Fig. 7 shows the dynamic gain of SLA

and the shape of the switching window under different control

pulsewidths under gain compression factor of . There

is apparently a gain depletion process right after the input of

the 0.6-ps control pulse. The shape of the switching windowis correspondingly distorted, with a big cusp in the primary

window and a small secondary window afterwards.

Fig. 8 shows the effect of the intraband processes on the BER

performance of the demultiplexed signal in the same system.

Neglecting the intraband processes, the narrower control pulse

results in the better BER performance. However, due to the exis-

tence of the intraband processes, the over narrow control pulse

could deteriorate the BER performance, especially when con-

sidering the signal timing jitter.

Fig. 9 shows the BER value versus the signal power detected

by the receiver under different values of compression factor and

signal timing jitter. The control pulsewidth is 0.6 ps. It confirms

Fig. 9. BER performance versus received signal power in the same 40 2 10Gb/s situation with and without consideration of nonlinear gain compression, inwhich ps.

that the combination of intraband processes and signal timing

jitter can destroy the BER performance. If the signal timingjitter is negligible, the distorted switching window can only en-

hance the channel crosstalk to a certain extent, which is shown

as a small power penalty. However, in practice, because of the

inevitable signal timing jitter, the secondary window will seri-

ously deteriorate the BER performance and finally boost up the

error floor.

Therefore, nonlinear gain compression must be considered

for SLA-based all-optical switches in terahertz OTDM applica-tions. Furthermore, it brings about much stricter limit on timing

jitter of the pulses, which corresponds to stricter requirements

on the system designs. That is one of the main reasons why

the narrowest switching window reported with a SLALOM was

just 4 ps, until now [2]. Even though a subpicosecond switchingwindow has been realized with a MachZehnder structure [22],

no reports of acceptable BER performance have been published.

V. CONCLUSION

In this paper, we comprehensively analyze the demultiplexing

performance of the SLALOM device in OTDM systems. Above

all, the SLA is the key element for guaranteeing the switching

performance. An SLA with higher linewidth enhancement

factor is beneficial to get higher output power. The injection

current of the SLA should be specifically adjusted to obtain a

flat and high switching window.

There is a compromise in switching window width betweenthe channel crosstalk induced by the finite carrier lifetime and

the inevitable timing jitter in the received signal pulses. The op-

timal switching window width should be slightly wider than half

of the pulse interval of the OTDM signal. The upper limit of the

control pulsewidth is about 1/3of the OTDM bitinterval in order

not to restrict the BER performance. In a practical design, it is

suggested to adopt the combination of higher channel number

and lower single channel bitrate, which has better tolerance to

the timing jitter of the signal pulses.

All of these conclusions can be extended to various SLA-

based interferometric switches and are instructive for subtera-

hertz OTDM system design. Furthermore, compared with fiber-
http://-/?-http://-/?-http://-/?-http://-/?-

8/13/2019 00996589

7/7


based switches, the SLA-based switches are inherently insensi-

tive to the signal timing jitter, which is a merit in practical ap-

plications.

For terahertz OTDM applications, the nonlinear gain

compression originating from carrier heating and spectral

hole burning cannot be ignored. The interaction between the

distorted switching window induced by the intraband processes

and the signal timing jitter will seriously raise the error floorand, in the worse case, will prevent the demultiplexed signal

from being readable. Therefore, SLA-based all-optical switches

cannot be used in terahertz OTDM applications.

ACKNOWLEDGMENT

The author wishes to thank D. Cohen and P. Royo at Univerity

of CaliforniaSanta Barbara for fruitful discussions and Prof.

J. Lin at Beijing University of Posts and Telecommunications.

REFERENCES

[1] J. P. Sokoloff, P. R. Prucnal, I. Glesk, andM. Kane, A Terahertz OpticalAsymmetric Demultiplexer (TOAD),IEEE Photon. Technol. Lett., vol.15, pp. 787790, July 1993.

[2] I. Glesk, J. P. Sokoloff, and P. R. Prucnal, Demonstration of all-opticaldemultiplexing of TDM data at 250 Gbit/s, Electron. Lett., vol. 30, pp.339340, Feb. 1994.

[3] J. P. Sokoloff, I. Glesk, P. R. Prucnal, and P. K. Boncek, Performanceof a 50 Gbit/s optical time domain multiplexed system using a TerahertzOptical Asymmetric Demultiplexer, IEEE Photon. Technol. Lett., vol.6, pp. 98100, Jan. 1994.

[4] K. Suzuki, K. Iwatsuki, S. Nishi, and M. Saruwatari, Error-free demul-tiplexing of 160 Gbit/s pulse signal using optical loop mirror includingsemiconductor laser amplifier,Electron. Lett., vol. 30, pp. 15011503,Sept. 1994.

[5] K. H. Ahn, M. Vaziri, B. C. Barnett, G. R. Williams, X. D. Cao, M.N. Islam, B. Malo, K. O. Hill, and D. Q. Chowdhury, Experimentaldemonstration of a low-latency fiber soliton logic gate, J. LightwaveTechnol., vol. 14, pp. 17681775, Aug. 1996.

[6] N. J. Doran and D. Wood, Nonlinear-optical loop mirror, Opt. Lett.,vol. 13, no. 1, pp. 5658, 1988.

[7] M. Nakazawa, E. Yoshida, T. Yamamoto, E. Yamada, and A. Sahara,TDM single channel 640 Gbit/s transmission experiment over 60 kmusing a 400 fs pulse train and a walk-off free, dispersion-flattened non-linear optical loop mirror, Electron. Lett., vol. 34, pp. 907908, Apr.1998.

[8] S. B. Alleston, P. Harper, I. S. Penketh, I. Bennion, and N. J. Doran,1220 km propagation of 40 Gbit/s single channel RZ data overdispersion managed standard (nondispersion shifted) fiber, in Proc.OFC/IOOC99, San Diego, CA, 1999, PD3, pp. PD3/1PD3/3.

[9] V. Kaman, A. J. Keating, S. Z. Zhang, and J. E. Bowers, SimultaneousOTDM demultiplexing and detection using an electroabsorption modu-lator,IEEE Photon. Technol. Lett., vol. 12, pp. 711713, June 2000.

[10] R. Hess and M. Caraccia-Grosset al., All-optical demultiplexing of 80to 10 Gb/s signals with monolithic integrated high-performance Mach-Zehnder interferometer, IEEE Photon. Technol. Letters, vol. 10, pp.165167, Jan. 1998.

[11] S. Diez, C. Schubert, R. Ludwig, H. J. Ehrke, U. Feiste, C. Schmidt, andH. G. Weber, 160 Gbit/s all-optical demultiplexer using hybrid gain-transparent SOA Mach-Zehnder interferometer,Electron. Lett., vol.36,pp. 14841486, Aug. 2000.

[12] A. D. Kersey, M. J. Marrone, and M. A. Davis, Polarization-insensi-tive fiber optic Michelson interferometer, Electron. Lett., vol. 27, pp.518520, Mar. 1991.

[13] D. Zhou, K. Kang, I. Glesk, and P. Prucnal, An analysis of signal-to-noise ratio and design parameters of a Terahertz Optical Asymmetric

Demultiplexer,J. Lightwave Technol., vol. 17, pp. 298307, Feb. 1999.[14] J. M. Tang, P. S. Spencer, and K. A. Shore, Influence of fast gain deple-tion on the dynamic response of TOADs, J. Lightwave Technol., vol.16, pp. 8691, Jan. 1998.

[15] K. Uchiyama, T. Morioka, S. Kawanishi, H. Takara, and M. Saruwatari,Signal-to-noise ratio analysis of 100 Gbit/s demultiplexing using non-linear optical loop mirror,J. Lightwave Technol., vol. 15, pp. 194201,Feb. 1997.

[16] H. X. Shi and J. T. Lin, Theoretical analysis on polarization deviationand switchwindow optimizationin nonlinear optical loop mirror demul-tiplexer, J. Lightwave Technol., vol. 17, pp. 25722576, Dec. 1999.

[17] N. A. Olsson, Lightwave systems with optical amplifiers,J. LightwaveTechnol., vol. 7, pp. 10711082, July 1989.

[18] G. P. Agrawal,Nonlinear Fiber Optics, 2nd ed. New York: Academic,1995, ch. 11, pp. 471530.

[19] R. J. Manning, A. E. Kelly, A. J. Poustie, and K. J. Blow, Wavelengthdependence of switching contrast ratio of semiconductor optical ampli-

fier-based nonlinear loop mirror,Electron. Lett., vol. 34, pp. 916918,Apr. 1998.[20] G. Swift, Z. Ghassemlooy, A. K. Ray, and J. R. Travis, Modeling of

semiconductor laser amplifier for the Terahertz Optical Asymmetric De-multiplexer,IEE Proc. Circuits Devices Syst., vol. 145, no. 2,pp. 6165,1998.

[21] K. I. Kang, T. G. Chang, I. Glesk, and P. R. Prucnal, Comparison ofSagnac and Mach-Zehnder ultrafast all-optical interferometric switchesbasedon a semiconductor resonant optical nonlinearity,Appl. Opt., vol.35, no. 1, pp. 417426, 1996.

[22] S. Nakamura, Y. Yeno, and K. Tajima, Ultrafast (200-fs switching, 1.5Tb/s demultiplexing) and high-repetition (10 GHz) operations of a po-larization-discriminating symmetric Mach-Zehnder all-optical switch,

IEEE Photon. Technol. Lett., vol. 10, pp. 15751577, Nov. 1998.

Hanxing Shi (S98M01) was born in InnerMongolia, China, in 1973. She received the B.S.degree in physics from Beijing Normal University,Beijing, China, in 1994 and the Ph.D. degree inelectrical engineering from Beijing University ofPosts and Telecommunications, Beijing, China, in1999.

From 1999 to 2001, she worked as a PostdoctoralResearcher at the University of California, SantaBarbara. She is currently with Yotta Networks, Inc.,Dallas, TX. Her research interests include photonic

switching, optical networking, WDMOTDM technologies and optical testing.

00996589

Documents