11 - analysis of modulation format in the 40gbs optical communication system

8/22/2019 11 - Analysis of Modulation Format in the 40Gbs Optical Communication System

1/8

OpticsOptikptik

Optik ] (]]]]) ]]]]]]

Analysis of modulation format in the 40 Gbit/s opticalcommunication system

Aihan Yina,b,, Li Lib, Xinliang Zhanga

aInstitute of Optoelectronics Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, ChinabSchool of Information Engineering, East China Jiaotong University, Nanchang 330013, China

Received 12 October 2008; accepted 6 February 2009

Abstract

Three different modulation formats including nonreturn-to-zero (NRZ), return-to-zero (RZ), carrier-suppressed

return-to-zero (CS-RZ) and the differential phase keying (DPSK) modulation format of each code are introduced in

the article. A method of their modulated signal generation with computer is described, and a comparison of their

spectra and waveforms is made. The 40 Gbps signal transmitted in 200 km G.652 fiber by way of single channel with

erbium-doped-fiber-amplifier (EDFA) is simulated for these three formats. The ability of anti-dispersion and anti-

PMD is analyzed. It is shown that RZ and CS-RZ formats are more tolerant than NRZ format in the same conditions.

Crown Copyright r 2009 Published by Elsevier GmbH. All rights reserved.

Keywords: Optical communication; Modulation format; NRZ; RZ; CS-RZ

1. Introduction

With the rapid development of the next generation of

optical fiber transmission information system, 40 Gbps

optical fiber transmission system and its wavelength-

division multiplexing (WDM) system have been the

focus of research. In order to enhance the capacity of the

system and diminish the degradation of performance,

which would be caused by the loss of transmission,

systems engineering and optimization would be impor-tant. Thereinto the optical code pattern would be the

important factor deciding spectrum efficiency, transmis-

sion quality and dispersive tolerance of the system.

Thus, the chosen code pattern is the first factor in the

high-speed optical transmission system [1,2].

The application of an optical fiber transmission

system and a dense-wavelength-division-multiplexing

system markedly decreases dispersive tolerance, and

the non-linearity effect has an impact on system

performance. Traditional nonreturn-to-zero (NRZ)

code-pattern would not have met the demand, while

needing other new modulation formats. Many code-

patterns have been proposed in terms of a 40 Gb/soptical transmission system [311], such as return-to-

zero (RZ) [3], besides the RZ of the carrier suppressive

(CS-RZ), single sideband-RZ (SSB-RZ), duojdecimal-

RZ (D-RZ), mend duojdecimal-RZ (MD-RZ) [4],

RZDPSK [5,6], full spectrum return-to-zero (FSRZ)

and chirp return-to-zero (CRZ). DPSK and RZ are

better than NRZ in terms of anti-noise. RZDPSK is

better than NRZ in influencing anti-dispersive charac-

ter. CS-RZ, CRZ and DPSK are better than NRZ in

ARTICLE IN PRESS

www.elsevier.de/ijleo

0030-4026/$ - see front matter Crown Copyrightr 2009 Published by Elsevier GmbH. All rights reserved.

doi:10.1016/j.ijleo.2009.02.021

Corresponding author at: Institute of Optoelectronics Science and

Engineering, Huazhong University of Science and Technology, Wuhan

430074, China.

E-mail address: [email protected] (A. Yin).

Please cite this article as: A. Yin, et al., Analysis of modulation format in the 40 Gbit/s optical communication system, Opt. Int. J. Light Electron.

Opt. (2009), doi:10.1016/j.ijleo.2009.02.021
http://www.elsevier.de/ijleohttp://localhost/var/www/apps/conversion/tmp/scratch_10/dx.doi.org/10.1016/j.ijleo.2009.02.021mailto:[email protected]://localhost/var/www/apps/conversion/tmp/scratch_10/dx.doi.org/10.1016/j.ijleo.2009.02.021http://localhost/var/www/apps/conversion/tmp/scratch_10/dx.doi.org/10.1016/j.ijleo.2009.02.021mailto:[email protected]://localhost/var/www/apps/conversion/tmp/scratch_10/dx.doi.org/10.1016/j.ijleo.2009.02.021http://www.elsevier.de/ijleo


2/8

terms of non-linear effect. SSB is better than NRZ in

terms of spectrum effectiveness. Recently, some code-

patterns have been studied, which include differential

quadrature phase keying (DQPSK) [7], intensity mod-

ulation-DPSK (IM-DPSK) [8] and the prefiltered

CS-RZ [9]. NRZDPSK, RZDPSK and CS-RZ

DPSK use the phase change of the close codes showingsignals 0 and 1. Their spectra are smooth and do

not have any linear spectrum. IM-DPSK should

diminish the optical intensity change of close codes, in

order to decrease chatter and non-linearity. Differential

quadrature phase keying (DQPSK) makes the phase

change in the code of 2 bytes. Prefiltered CS-RZ is used

to filter the CS-RZ in order to decrease the width of the

spectrum and enhance spectrum efficiency.

In this paper, consider, for example, 40 Gbps , the

way of modelization of NRZ, RZ and CS-RZ with

computer analyses the optical spectrum. The 40 Gbps

signal transmitted in the 200 km G.652 fiber using a

single channel with erbium-doped-fiber-amplifier

(EDFA) is simulated for these three formats. Thus, we

can obtain a better code-pattern with high spectrum

efficiency and high tolerance for optical noise and non-

linearity effect.

2. The principle and characteristic of the

code-pattern

2.1. The principle of chosen code-pattern

Three principles should be followed for the modula-

tion format: firstly, the compact modulation signal

spectrum should be good at enhancing the operating

factor of the spectrum and the dispersive tolerance of

group velocity; secondly, non-linearity tolerance should

be high; thirdly, the structure of the transmitter and

receiver should be simple.

2.2. The principle of NRZ

We usually use the MachZehnder modulator (MZM)

and the consecutive wave (CW) laser in the modulationsystem. Except for the NRZ, their appearance would be

performed by the two concatenations of MZM. These

two concatenations of MZM play different roles. The

first MZM is used to bring various pulses by the drive of

the clock signal. The second one is used to load the data.

Fig. 1 shows the frame of the NRZ signal of the

optics. When 1 is transmitted in the NRZ, optical

signal impulse occupies a whole bit-time; when there is

no optical pulse, the signal is 0. The realization of the

coding is simple, only needing a high-speed exteriormodulator that can work effectively at the speed of

10 Gbps. The advantages of NRZ are the simplicity of

application, low cost and high spectrum efficiency,

which can be used widely in synchronous digital

hierarchy (SDH) and wavelength-division-multiplexing

systems. Under an ~10 Gbps system, we use the NRZ

modulation model. The disadvantage of NRZ is that the

transition does not return to zero between two codes,

the sensitivity for transmission loss. Therefore, it is not

suitable for high-speed and extra long-distance trans-

mission.

2.3. The principle of RZ and CS-RZ

Fig. 2 shows the frame of the principle of the

generation of RZ and CS-RZ, which is composed of

the two concatenations of MZM. The technology of RZ

code has come up recently, which is used in high-speed

40Gps optical transmission systems. In the pulse

sequence of the RZ code, the transition area that

connects 1 amplitude of electric field has an indepen-

dent time envelope. Because the modulation format of

RZ has a different transition all the time in the code bits,

it can bring more neatness optical signal in order to

unscramble the receiver. The advantage of RZ is the low

average of optical power and higher ability for anti-non-

linearity effect and anti-polarization mode dispersion

(PMD) [12]. The RZ code is also more conducive to

clock recovery. Because the consecutive 1 of NRZ is a

whole, the eye pattern of RZ code stretches more, the

anti-error-code performance becomes better, and im-

proves the 3 dB of the optical signal-to-noise ratio

(OSNR).

The CS-RZ code is based on the traditional RZ code,

and joins the phase separation ofp in each adjacent sign

bit (irrespective of whether the sign bit is 0 or 1).

The phase separation of the carrier can be regarded asthe signal with a minus but the carrier is invariable. The

typical value of this signal with positive and negative

ambipolar is 0, so there is no pinnacle in the zero

ARTICLE IN PRESS

CW-Laser MZM

40Gb/s

optical NRZ

40Gb/s

eletrical NRZ

Fig. 1. Blocks diagram of NRZ.

CW-Laser MZM

40Gb/soptical RZ

40Gb/seletrical RZ

MZM

40Gb/sclock RZ

Bias

Fig. 2. Blocks diagram of RZ/CS-RZ.

A. Yin et al. / Optik ] (]]]]) ]]]]]]2


Opt. (2009), doi:10.1016/j.ijleo.2009.02.021
http://localhost/var/www/apps/conversion/tmp/scratch_10/dx.doi.org/10.1016/j.ijleo.2009.02.021http://localhost/var/www/apps/conversion/tmp/scratch_10/dx.doi.org/10.1016/j.ijleo.2009.02.021


3/8

frequency because without D function (impulse func-

tion), after multiplying the corresponding carrier, there

is also no pinnacle in the carrier. In the CS-RZ, because

the sign about the consecutive code of amplitude of the

electric field is reversed, we can obtain the low width of

spectrum. The high power not only increases the

dispersive capacity but also enhances the resistance ofthe non-linearity of self-phase modulation (SPM), four-

wave-mixing (FWM), etc.

3. Code-type wave shape and spectral analysis

3.1. Wave analysis of code type

At present, we often use MZM to produce the

modulation code; MZM is the ~two interconnected

3 dB coupler. While a DL optical path difference exists

between two wave-guides, there can be phase modula-tion produced by the two signals at the output. As

shown in Fig. 1, with the MachZehnder interferometer

(MZI) modulator modulating for the CW laser lamp-

house, the electric 40 Gbps NRZ signal (27-1 pseudo-

random binary sequence) would become a 40 Gbps

NRZ optical signal. For Fig. 2, the first MZI has the

same working theory as MZI of Fig. 1, the only change

is the electric 40 Gbps of NRZ into RZ (duty factor is

0.5); the second MZI should be controlled by the sine-

wave clock and voltage bias on two spur tracks of MZI,

getting through to modulate the amplitude, frequency,

phase and the voltage bias, so as to obtain the optical

signal of RZ and CS-RZ.

Thus, we might as well input light field:

Eint jE0jejoct (1)

After passing the MZM, after the phase modulation,

the light field would be

Eoutt Eint

2ejj1t ejj2t (2)

j1t p

2

1

VpV1m sino1t C1 V1 (3)

j2t p2

1Vp

V2m sino2t C2 V2 (4)

where the Vim, oi( 2fip) and Ci (i 1, 2) are the

amplitude, angular frequency and phase of the clock

signal on two spur track of MZI, respectively. V1, V2can provide the voltage bias on two spur track of MZI

separately. When the single arm works causing

the appearance of phase separation, Vp

is the switch

voltage from the max to the min. In order to make

the MZM work at the station without chirp, we can

add the voltage of two single arms to a fixed voltage

bias. That is V1 (t)+V2(t) Vbias; thus the output of

the light field is

Eoutt Eint cosp

2VpVin Vbias

ejpVbias=2V (5)

The output of the light intensity is

Poutt Pint cos2 pVin Vbias

2Vp

(6)

The RZ code with dutyfactor 50% can set the input of

the electrical clock signal as

Vin Vp

2sin o0t; the bias voltage is

Vp

2(7)

Then the light field and light intensity of RZ can be

derived from Eqs. (3) and (4):

Eoutt Eint cosp

2sin o0t

(8)

Pout

t Pint

21 cosp sin o

0t (9)

In the above formulae, the optical impulse cycle is

2p/o0, the angle frequency is o0and the full-width at

half-maximum (FWHM) is p/o0.

The CS-RZ code would be set as the input of electri-

cal clock signal, where Vin Vp sino0t and the voltage

bias is Vp

Eoutt Eint cosp

2VpVp sin o0t Vp

ejp=2 (10)

Poutt Pintsin2 p

2sin o0t (11)

In the above formula, the optical impulse cycle is

p/o0, angle frequency is 2o0 and the FWHM is 2p/3o0.

3.2. Optical spectrum analysis of the code-pattern

According to the above theoretical expression

of various code-models, using the method of optical

spectrum towards random signal in the communication

theory, the power spectrum density of the random pulse

sequence divides into two parts: consecutive spectrum

[Pu(o)] and linear-spectrum [Pv(o)]. By computing, the

power spectrum of the NRZ code is given by

PEf 12Tssapfc fTs

2 12dfc f (12)

Pf f0

X1N0

J2n1p

2

2n 1f02pf fcf fc

2 2n 12f20

(

cospf fc

2f0

2X1

1

df fc 2n 1f0

(13)

From the above analysis, it is seen that the CS-RZ

optical spectrum has a 40 GHz distance of stair linear-

spectrum. No linear-spectrum existed, which is because

ARTICLE IN PRESS

A. Yin et al. / Optik ] (]]]]) ]]]]]] 3


Opt. (2009), doi:10.1016/j.ijleo.2009.02.021


4/8

of the change of p phase between the two pulses. The

power spectrum of the RZ code is

gt ejp=4 J0p

4

2

X1n1

J2np

4

cos2nomt

(

2X1n0

J2n1p

4

sin2n 1o0t

)

df fc 2nf0 (14)

The expression of the RZ optical spectrum shows that

the linear spectrum exists in the RZ optical spectrum.

From Table 1 and this formula, the FWHM of theNRZ signal is 25 ps, the FWHM of RZ is 12.5 ps and the

CS-RZ is 12.5ps. Figs. 35 show the spectrum of

modulation format. Fig. 3 shows the wave and the

spectrum of NRZ; the spectrum width of NRZ is about

80 GHz (the distance between secondary line spectrum).

Fig. 4 shows the wave and the spectrum of the RZ code,

and the spectrum width is 160 GHz. Fig. 5 shows the

wave and the spectrum of the CS-RZ code, and the

spectrum width is 120 GHz with no carrier wave. This

section, by comparing the NRZ, RZ and CS-RZ

between the single pulse wave and the spectrum, obtains

the concrete transmission characteristic of variousmodulation formats [5,10].

3.3. Analysis of spectrum by three kinds of

modulation formats

The impulse width of NRZ is the largest in these six

kinds of modulation formats, and so intersymbol

interference easily occurs, is sensitive to transmission

loss, influencing the non-linear effect, but the spectrum

of NRZ is narrow, which is good for decreasing the

interference of the inter-channel WDM system.

The dutyfactor of the RZ code will reduce; impulse

width is smaller than NRZ, which can restrain the non-

linear effect of optical fiber, suitable to work in the high-

power and long-distance transmission condition. How-

ever, the spectrum of RZ code is wide and dispersive

capacity decreases markedly, which is not good for

management.

The impulse width of CS-RZ is smaller than NRZ; the

spectrum width is between the NRZ and RZ. Part of the

carrier wave is blocked, thus it not only becomes smaller

and increases the dispersive capacity but also becomes

stronger in its ability to resist the non-linear effect.

ARTICLE IN PRESS

Fig. 3. Wave and spectrum of NRZ: (a) wave of NRZ; (b)

spectrum of NRZ and (c) spectrum of NRZDPSK.

Table 1. Parameter of selected RZ and CS-RZ.

Type V1m V1m F1 (GHz) F2 (GHz) C1 C2 V1 V2

RZ Vp

Vp

40 40 180 0 Vp

Vp

CS-RZ Vp

Vp

20 20 180 0 Vp

0

A. Yin et al. / Optik ] (]]]]) ]]]]]]4


Opt. (2009), doi:10.1016/j.ijleo.2009.02.021


5/8

ARTICLE IN PRESS

Fig. 4. Wave and spectrum of RZ: (a) wave of RZ; (b)

spectrum of RZ and (c) spectrum of RZDPSK.

Fig. 5. Wave and spectrum of CS-RZ: (a) wave of CS-RZ; (b)

spectrum of CS-RZ and (c) spectrum of CS-RZDPSK.

A. Yin et al. / Optik ] (]]]]) ]]]]]] 5


Opt. (2009), doi:10.1016/j.ijleo.2009.02.021


6/8

The spectrum of NRZ is the most compact in the one-

lever sideband and baseband, which results in the cost of

eye pattern stretch becoming smaller comparatively

caused by the wave variation and the interference.

Because the NRZ spectrum contains the residual carrier

element, it would be affected by the FWM interference

in the low dispersive optical fiber.The spectrum of RZ has the linear-spectrum ob-

viously in the one-lever sideband and baseband; the one-

lever sideband will overlap in the adjacent channel of the

WDM system, which has a minor interval. So it can

arouse badly interference between the adjacent channels.

Then its optical spectrum width is bigger than NRZ and

CS-RZ so as not to assure the optical efficiency in the

receiver.

In parallel to NRZ, the optical spectrum shape of

CS-RZ is prohibited in the frequency element of a

carrier wave. But two interval linear-spectra with a

period of a byte frequency appeared, which is 40 GHz in

this article. When the frequency interval of the WDM

channel is greater than 100 GHz, this characteristic can

diminish the loss of FWM, but it can result in serious

loss of FWM when the frequency interval is 75 GHz.

The spectrum width of CS-RZ is between NRZ and RZ.

In the baseband and first-order sideband which do not

conclude the linear-spectrum element, three kinds of

DPSK signals have no pinnacle because of itself

characteristic, which can prohibit the non-linear effect

in the optical fiber such as FWM and SRS. In terms of

spectrum shape, there are some successive performances

between the NRZDPSK and NRZ, RZDPSK and

RZ, and CS-RZDPSK and CS-RZ. The spectrumwidth of NRZDPSK is the smallest, followed by CS-

RZDPSK and RZDPSK is the biggest.

4. Analysis of transmission performance

4.1. Performance of anti-dispersive code format

Different codes have different spectra; the widths of

various spectra determine the dispersion that has

different effects. Dispersion is the width of the pulse

wave caused by diverse waves transmitted in the optical

fiber differently. When the pulse width is of a certain

extent, it affects the inter-code interference badly.

Towards the transmission system of 40 Gbps, we should

consider the anti-dispersion characteristic of different

codes [13]. As shown in Fig. 6, the anti-dispersion

characteristic of DPSK and RZ, NRZ is compared.

With the same input power, the peak value power of RZ

is two times that of NRZ; thus after the transmission of

optical fiber the RZ power can converge intensely.

However, since the power of NRZ is dispersive, using

the RZ code is good for enhancing the acceptable

sensitivity so as to decrease the requirement of OSNR

in the transmission system. We can conclude the

optimal optical anti-dispersive performance of RZ

DPSK (Fig. 5).

4.2. The anti-PMD ability of code format

In the standard single-mode optical fiber, the base

mode is composed of a couple of vertical polarization

modes. Only when it is located in the round symmetry

with a refractive index, the half of the whole opticalpower of each mode carrier transmits in the same speed

and arrives at the optical port simultaneously and

becomes a single mode. Because the practical fiber with

different refractive indexes is not isotropic, the speed of

the mode will be influenced. It can be transmitted with

different speeds to cause the dispersion of signals. This

phenomenon is called polarization mode dispersion.

PMD has a little effect on speed under 10 Gbps, which is

why it is not basically considered. Considering speeds of

10 Gbps and above, the less-extrusive polarization mode

dispersion can become the key factor in limiting the

performance of the system [14]. When the speed of the

single channel comes to 40 Gbps, polarization mode

dispersion would give rise to the high-level effect

obviously, which has a severe effect on the transmission

performance of the system. Assuming the power of

PMD to be 1 dB, the 10 Gbps non-electric relay system

has the maximum transmission distance of 200 km; thus

correspondingly, the 40 Gbps system has only 25 km

distance, and so the linear modulation code should

consider the ability of anti-PMD dispersion effect. The

anti-PMD performance of each code is compared below,

as shown in Fig. 7. From the comparison we can

conclude that RZ code has the best ability of anti-PMD.

ARTICLE IN PRESS

0

-1

0

1

2

3

4

5

6

7

8

RZ

RZ-DPSK

NRZ

NRZ-DPSK

V2*L*D[104 (GHz)2]

2 4 6 8 10

PowerPenalty

(dB)

Fig. 6. The contrast of some different modulate methods.

A. Yin et al. / Optik ] (]]]]) ]]]]]]6


Opt. (2009), doi:10.1016/j.ijleo.2009.02.021


7/8

5. The format of transmission system and the

results of simulations

The system should be configured for simulations. Thetransmitter uses the CW laser, which has a wavelength

of 1550 nm. With the input MZM of NRZ electrical

signal generates the optical NRZ and can be sent to

the circuitry. The CS-RZ is composed of two MZM

concatenations: the first one produces the NRZ and is

sent to the second level; from the output CS-RZ of the

second level and the second MZM modulator, the RF

port transmits the sin clock signals when the transmis-

sion speed is half. The transmission speed is 40 Gbps

and the signal sequence is 27-1. The transmission optical

fiber is composed of five different single-mode fibers

(SMFs) with the length of 50 km, and the whole length is

250km. The dispersion compensation uses the disper-

sion compensation fiber (DCF). The parameter of SMF

and DCF is shown in Table 2. The various simulations

of codes are shown in Fig. 8.

The best remaining dispersion of NRZ is 10 ps/nm;

the dispersion capacity of 1 dB Q value is 60 ps/nm.

Owing to the bad performance of the system, when the

Q value is 16.9dB (BER 1012), the remaining

dispersion scope is 45 ps/nm. When using the CS-RZ

code, the best remaining dispersion is 15 ps/nm, and

the dispersion capacity of 1 dB Q value is 60 ps/nm,

which is the same as the NRZ code. But when Q is

16.9 dB with good performance of the system, the scope

of the remaining dispersion is 100 ps/nm. Irrespective of

whether we use the NRZ or CS-RZ, the dispersion

capacity of the system is also extraordinary small. Thus,

accurate dispersion management is absolutely necessa-

rily in the 40 Gbps transmission system. We can get the

eye pattern through the computer simulations, which are

ARTICLE IN PRESS

0.0-1

0

1

2

3

45

6

7

8

9

10

11

Powerpenalty(dB)

Date/T

NRZ

NRZ-DPSK

RZ

RZ-DPSK

0.2 0.4 0.6 0.8

Fig. 7. The contrast of anti-disperse of PMD.

Table 2. Parameter of SMF and DCF.

Item name SMF DCF

Attenuation (dB/m) 0.275 0.625

Disperse (ps/nm km) 17 85

Disperse slope (ps/nm2 km) 0.058 0.029

Available area (mm2) 80 14.4

Non-linearity index (1020 m2/W) 2.5 3.2

Fig. 8. The figure of receiver (Q 6): (a) the figure of receiver

(NRZ); (b) the figure of receiver (RZ) and (c) the figure of

receiver (CS-RZ).

A. Yin et al. / Optik ] (]]]]) ]]]]]] 7


Opt. (2009), doi:10.1016/j.ijleo.2009.02.021


8/8

shown in Fig. 8. When Q is 6 from the eye pattern of the

receiver, we can get the same pattern between RZ and

CS-RZ, because they are also the RZ, and the difference

is only the dutyfactor between the two. The dutyfactor

of CS-RZ is bigger than the RZ, and the upper jitter of

NRZ is comparatively severe.

6. Conclusions

In this article, 40Gbps optical signals of three

modulation formats through computer simulation were

produced and its wave shape and optical spectrum were

compared. Then the performance of dispersion com-

pensation is simulated through the non-zero dispersion

shifted fiber by a single-channel transmission mode.

The following results are obtained: the ability of anti-

nonlinear and anti-PDM of RZ and CS-RZ is stronger

than NRZ under the complete dispersion compensationcondition. We can enhance the quality of transmission

through appropriate dispersion compensation. In the

future, we can carry out further research on the

following aspects: carry on further the research on

non-linear phenomena in the high-speed optical fiber

transmission and find a way of restraining them. Further

research on the dispersion management should be done

for better transmission performance.

References

[1] Xing Wei, Xiang Liu, Steven H. Simon, C.J. McIntyre,Intrachannel four-wave mixing in highly dispersed return-to-

zero differential-phase-shift-keyed transmission with a non-

symmetric dispersion map, Opt. Lett. 31 (1) (2006) 2931.

[2] Keang-Po Ho, Exact analysis of a balanced receiver for

differential phase-shift keying signals, Opt. Lett. 32 (5)

(2007) 472474.

[3] Takashi Mizuochi, Kazuyuki Ishida, Tatsuya Kobayashi,

et al., A comparative study of DPSK and OOK WDM

transmission over transoceanic distances and their per-

formance degradations due to nonlinear phase noise,

J. Lightwave Technol. 21 (9) (2003) 19331943.

[4] Jin-Xing Cai, Morten Nissov, Carl R. Davidson, et al.,

Long-haul 40 Gb/s DWDM transmission with aggregate

capacities exceeding 1 Tb/s, J. Lightwave Technol. 20 (12)

(2002) 22472258.

[5] Chris Xu, Xiang Liu, Linn F. Mollenauer, et al.,

Comparison of return-to-zero differential phase-shift

keying and ONOFF keying in long-haul dispersion

managed transmission, IEEE Photon. Technol. Lett. 15

(4) (2003) 617619.

[6] Takanori Inoue, Kazuyuki Ishida, Eiichi Shibano, et al.,

Experimental comparisons of DPSK and OOK in long

haul transmission with 10 Gb/s signals, DMF Span and

Raman Assisted EDFA.OFC, 2005, OThO2.

[7] Michael Ohm, Torsten Freckmann, Comparison of

different DQPSK transmitters with NRZ and RZ impulse

shaping, in: IEEE Workshop on Advanced Modulation

Formats, San Francisco, 2004, pp. 78.

[8] D. Kovsh, E.A. Golovchenko, A.N. Pilipetskii, Enhance-

ment in performance of long-haul DWDM systems via

optimization of the transmission format, OFC (2002)

361362.[9] Takehiro Tsuritani, Akira Agata, Itsuro Morita, et al.,

Ultra-long-haul 40-Gb/s-based DWDM transmission

using optically prefiltered CS-RZ signals, IEEE J.

Quantum Electron. 10 (2) (2004) 403411.

[10] T. Tsuritani, K. Ishida, A. Agata, et al., 70-GHz-spaced

40 42.7 Gb/s transpacific transmission over 9400km using

prefiltered CSRZDPSK signals, all-Raman repeaters,

and symmetrically dispersion-managed fiber spans, J.

Lightwave Technol. 22 (1) (2004) 22315538.

[11] Sven Kieckbusch, Sebastian Ferber, Harald Rosenfeldt, et

al., Automatic PMD compensator in a 160-Gb/s OTDM

transmission over deployed fiber using RZDPSK modu-

lation format, J. Lightwave Technol. 23 (1) (2005)

165172.[12] Zhang Qi, Chen Ming-hua, Chen Hong-wei, Zhang Ji-yu,

Adaptive PMD compensation experiment in 40Gb/s

CSRZ system, Optoelectron. Lett. 3 (3) (2007) 207210.

[13] Mikio Yagi, Shuichi Satomi, Shinya Tanaka, et al., Field

trial of automatic chromatic dispersion compensation for

40-Gb/s-based wavelength path protection, IEEE Photon.

Technol. Lett. 17 (1) (2005) 229237.

[14] Xiaoguang Zhang, Yuan Zheng, Yu Shen, et al., Particle

swarm optimization used as a control algorithm for

adaptive PMD compensation, IEEE Photon. Technol.

Lett. 17 (1) (2005) 8591.

ARTICLE IN PRESS

A. Yin et al. / Optik ] (]]]]) ]]]]]]8


Opt. (2009), doi:10.1016/j.ijleo.2009.02.021

11 - analysis of modulation format in the 40gbs optical communication system

Documents