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179 p. Due to the ever-increasing capacity requirement for communication networks, the number of wavelength-division multiplexing (WDM) channels and channel bit rate continue to increase in optical transmission systems. As a result, WDM channel spacing has to be reduced in order to accommodate more channels with higher bit rates, which in turn increases the impact of transmission impairments of optical fiber systems. These impairments include optical amplifier noise, group-velocity-dispersion (GVD), polarization-mode-dispersion (PMD), nonlinear effects such as self-phasemodulation (SPM), cross-phase-modulation (XPM), and four-wave-mixing (FWM), as well as their interaction with dispersion. These impairments may ultimately limit the distance capacity product of an optical transmission system. One technology that could improve the system performance under such impairments is to use advanced modulation formats rather than the conventional non-return-to-zero on-off-keying (NRZ-OOK). DOCTOR OF PHILOSOPHY (EEE)

This paper presents the generation and the performance evaluation of optical minimum shift keying (MSK) for high-speed and high-spectral-efficiency wavelength-division multiplexing systems. The detailed principle on optical MSK generation and detection is derived and analyzed. Optical MSK data (10.7 Gb/s) are successfully generated by an experiment using the proposed scheme. The results show that the optical MSK signal exhibits a very compact optical spectrum. The performance of the optical MSK modulated system is evaluated and compared with those of 50% duty-cycle return-to-zero differential phase shift keying (RZ-DPSK) and 50% duty-cycle return-to-zero on-off keying (RZ-OOK) modulated systems, via both simulation and experiment, in terms of dispersion tolerance, linear crosstalk, self-phase modulation (SPM) tolerance, stimulated Brillouin scattering (SBS) threshold, optimal receiver filter bandwidth, and optimal link launch power into single-mode fibers and dispersion compensation fibers. Experimental and simulation results show that the MSK signal exhibits the largest tolerance against fiber dispersion and SPM effect as compared with RZ-DPSK and RZ-OOK. Experimental results also confirm the negative penalty against the SPM effect. The SBS threshold of both the MSK and RZ-DPSK systems is more than 10 dB higher than that of the RZ-OOK system. The MSK that is generated with conventional carrier-suppressed return-to-zero (CSRZ) pulses exhibits a narrower optimal optical filter bandwidth but a wider electrical filter bandwidth compared with those of RZ-OOK and RZ-DPSK. The MSK signal that is generated with pure dual-mode pulses has a similar optimum range to RZ-OOK and RZ-DPSK at a high optical signal-to-noise ratio (OSNR) but has a narrower optimal optical filter bandwidth at a low OSNR. The optimum fiber launch power study shows that the MSK signal that is generated using the conventional CSRZ pulses exhibits higher optimum launch power, which agrees with the SPM tolerance study.

To avoid significant stimulated Brillouin scattering (SBS) generation in a bidirectional Raman-pumped long single-span transmission system, the SBS threshold is studied in both return-to-zero on-off -keying (RZ-OOK) and RZ differential phase-shift keying (DPSK) systems. It shows that SBS threshold in an RZ-DPSK system is more than 10 dB higher than that in an RZ-OOK system, and SBS reflection is dominated by copumping, while counterpumping has minor effect. Error-free eight-channel single-span transmission is demonstrated over 310-km standard single-mode fiber using RZ-DPSK format and bidirectional Raman pumping, without applying forward-error correction and remote-pumping techniques.

To extend transmission distance using cascaded in-line semiconductor optical amplifiers (SOAs) and differential phase-shift-keying modulation format, optimal operation conditions for SOAs, such as input power and operation current, are studied. 16/spl times/10.709-Gb/s wavelength-division-multiplexing transmission over 640-km SSMF with the optimal system design parameters is demonstrated. This is, to the best of our knowledge, the largest bit-rate distance product reported.

We have performed eight-channel wavelength-division-multiplexing transmission over 1050-km single-mode fiber using cascaded in-line semiconductor optical amplifier and differential phase-shift keying modulation format for the first time; more than 6 dB of power margin was achieved over forward-error correction threshold. Factors that affect the transmission performance were discussed. It was found that four-wave mixing is the main factor that limits the maximum transmission distance. Larger capacity distance product can be realized by further optimizing the configuration of transmission link.

We have demonstrated ten-stage cascaded wavelength conversion together with 800-km transmission for 10-Gb/s return-to-zero differential phase-shift keying (RZ-DPSK) format using four-wave mixing (FWM) in semiconductor optical amplifiers. To the best of our knowledge, this is the first experiment reported on cascade wavelength conversion for RZ-DPSK format, which cannot be realized by methods based on cross-gain modulation and cross-phase modulation using a semiconductor optical amplifier. Compared with wavelength conversion using FWM for conventional on-off keying format, the signal-to-pump ratio for RZ-DPSK format can be increased to higher level to achieve better performance.

Advanced InP technology is the enabling technology to achieve monolithic integrated 300-pin MSA compatible 43 Gb/s (RZ-)DQPSK transponder module with high performance. The integrated platform offers footprint, power, and cost reduction for next generation products.

Advanced InP technology is the enabling technology to achieve monolithic integrated 300-pin MSA compatible 43 Gb/s (RZ-)DQPSK transponder module with high performance. The integrated platform offers footprint, power, and cost reduction for next generation products.

DSDBR laser platform is enabling a comprehensive range of tunable products which are fuelling the drive towards flexible, wavelength agile networks. Laser/Modulator integrated platforms offer further footprint, power, and cost reduction for next generation products.

This paper examines the optimum optical and electrical filter bandwidths of the optical MSK receiver. Results show that the MSK signal with low OSNR exhibits narrower optimal optical filter bandwidth compared with RZ-DPSK and RZ-OOK.

Detailed principle for optical MSK generation and detection is presented. 10.7 Gb/s MSK data is transmitted and its dispersion tolerance is compared with that of RZ-DPSK and RZ-OOK. Results show that MSK exhibits better tolerance than other two formats.

Error free 8-channel single-span transmission is demonstrated over 310 km standard SMF using RZ-DPSK format and bidirectional Raman pumping, without applying FEC and remote-pumping techniques. (2 pages)

We evaluate the performance of the externally modulated optical minimum shift keying (MSK) signal. The tolerance against fiber dispersion, linear crosstalk, self phase modulation (SPM), and stimulated Brillouin scattering (SBS) threshold for MSK is studied and compared with that of 50% duty cycle return-to-zero differential phase shift keying (RZ-DPSK) and 50% duty cycle RZ on-off-keying (RZ-OOK), via both experiment and simulation. Simulation results show that the MSK signal has the widest tolerance against SPM and the smallest linear crosstalk among these formats. Experimental results agree with the simulation on negative penalty against SPM tolerance and show widest tolerance against dispersion tolerance for MSK. The measured SBS threshold of both MSK and RZ-DPSK is more than 10 dB higher than that of an RZ-OOK system.