System Modeling and Optimization in Phase-Modulated Optical Fiber Communication Systems

In this two-part study, the conclusions drawn from optimization of interferometer incoherent detection carried out by examining the effect of pre-emphasis within the electrical signal-driving path are examined first. This is an expansion upon a widespread industry standard as realized by the Oclaro group. System performance in tight optical filtering conditions can be improved with concurrent adjustments to the level of pre- emphasis and breadth of the delay-line interferometer free-spectral range. In the second study, we implement a dual-polarization quadrature phase-shift keyed modulation format with a digital signal processing block based upon the constant modulus algorithm realized via a feed-forward equalizer with and without the moving average method. Ultimately, the purpose of both studies is to study the efficacy of new modulation formats to enhance gains in spectral efficiency and improve robustness against chromatic dispersion within the optical fiber

Nonlinear Optical Signal Processing for Tbit/s Ethernet Applications

We review recent experimental demonstrations of Tbaud optical signal processing. In particular, we describe a successful 1.28 Tbit/s serial data generation based on single polarization 1.28 Tbaud symbol rate pulses with binary data modulation (OOK) and subsequent all-optical demultiplexing. We also describe the first error-free 5.1 Tbit/s data generation and demodulation based on a single laser, where a 1.28 Tbaud symbol rate is used together with quaternary phase modulation (DQPSK) and polarization multiplexing. The 5.1 Tbit/s data signal is all-optically demultiplexed and demodulated by direct detection in a delay-interferometer-balanced detector-based receiver, yielding a BER less than 10−9. We also present subsystems making serial optical Tbit/s systems compatible with standard Ethernet data for data centre applications and present Tbit/s results using, for instance silicon nanowires

Novel high-speed optical transmitters for optical frequency shift keying and inverse-return-to-zero signals.

Pun Siu Sun.Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.Includes bibliographical references (leaves 55-58).Abstract in English and Chinese.ABSTRACT --- p.ii摘要 --- p.ivChapter 1 --- BLACKGROUND AND INTRODUCTION --- p.1Chapter 1.1 --- OPTICAL FREQUENCY SHIFT KEYING (FSK) --- p.1Chapter 1.1.1 --- Basic concepts --- p.1Chapter 1.1.2 --- Applications --- p.3Chapter 1.2 --- MODULATION FORMATS --- p.6Chapter 1.3 --- ORTHOGONAL MODULATION --- p.9Chapter 1.4 --- THESIS ORGANIZATION --- p.11Chapter 2 --- A NOVEL OPTICAL FREQUENCY SHIFT KEYING TRANSMITTER BASED ON POLARIZATION MODULATION --- p.12Chapter 2.1 --- EXISTING OPTICAL FSK TRANSMITTER DESIGNS --- p.12Chapter 2.1.1 --- Optical FSK transmitter based on complementary intensity modulation --- p.12Chapter 2.1.2 --- Optical FSK transmitter based on direct modulation in a DFB laser --- p.13Chapter 2.1.3 --- Optical FSK transmitter based on single side-band (SSB) modulation technique --- p.15Chapter 2.1.4 --- Optical Continuous-Phase FSK (CPFSK) transmitter based on asymmetric Mach-Zehnder modulator --- p.17Chapter 2.1.5 --- Optical FSK transmitter based on phase modulation --- p.18Chapter 2.1.6 --- Summary --- p.20Chapter 2.2 --- PROPOSED OPTICAL FSK TRANSMITTER BASED ON POLARIZATION MODULATION --- p.21Chapter 2.3 --- EXPERIMENTAL DEMONSTARTION --- p.23Chapter 2.4 --- SYSTEM PERFORMANCE --- p.25Chapter 2.5 --- SUMMARY --- p.27Chapter 3 --- OPTICAL RETURN-TO-ZERO FREQUENCY SHIFT KEYING (RZ-FSK) (RZ-FSK) --- p.28Chapter 3.1 --- INTRODUCTION AND MOTIVATION --- p.28Chapter 3.2 --- PREVIOUS NRZ vs. RZ COMPARISON --- p.30Chapter 3.3 --- RZ-FSK TRANSMITTER DESIGN --- p.32Chapter 3.4 --- PERFROMANCE COMPARISON --- p.33Chapter 3.4.1 --- Back-to-back performance --- p.34Chapter 3.4.2 --- Chromatic dispersion tolerance --- p.35Chapter 3.4.3 --- Fiber nonlinearity tolerance --- p.38Chapter 3.5 --- SUMMARY --- p.41Chapter 4 --- A NOVEL OPTICAL TRANSMITTER FOR HIGH-SPEED DIFFERENTIAL PHASE SHIFT KEYING/INVERSE RETURN-TO-ZERO (DPSK/INV-RZ) ORTHOGONALLY MODULATED SIGNALS --- p.42Chapter 4.1 --- INTRODUCTION --- p.42Chapter 4.2 --- PREVIOUS SCHEME --- p.43Chapter 4.3 --- PROPOSED TRANSMITTER DESIGN --- p.45Chapter 4.4 --- EXPERIMENT AND RESULTS --- p.47Chapter 4.5 --- CONCLUSION --- p.51Chapter 5 --- SUMMARY --- p.52Chapter 5.1 --- THESIS SUMMARY --- p.52Chapter 5.2 --- FUTURE WORK --- p.53LIST OF PUBLICATIONS --- p.54REFERENCES --- p.5

Detection and processing of phase modulated optical signals at 40 Gbit/s and beyond

This thesis addresses demodulation in direct detection systems and signal processing of high speed phase modulated signals in future all-optical wavelength division multiplexing (WDM) communication systems where differential phase shift keying (DPSK) or differential quadrature phase shift keying (DQPSK) are used to transport information. All-optical network functionalities -such as optical labeling, wavelength conversion and signal regeneration- are experimentally investigated. Direct detection of phase modulated signals requires phase-to-intensity modulation conversion in a demodulator at the receiver side. This is typically implemented in a one bit delay Mach-Zehnder interferometer (MZI). Two alternative ways of performing phase-to-intensity modulation conversion are presented. Successful demodulation of DPSK signals up to 40 Gbit/s is demonstrated using the proposed two devices. Optical labeling has been proposed as an efficient way to implement packet routing and forwarding functionalities in future IP-over-WDM networks. An in-band subcarrier multiplexing (SCM) labeled signal using 40 Gbit/s DSPK payload and 25 Mbit/s non return-to-zero(NRZ) SCM label, is successfully transmitted over 80 km post-compensated non-zero dispersion shifted fiber (NZDSF) span. Using orthogonal labeling, an amplitude shift keying (ASK)/DPSK labeled signal using 40 Gbit/s return-to-zero (RZ) payload and 2.5 Gbit/s DPSK label, is generated. WDM transmission and label swapping are demonstrated for such a signal. In future all-optical WDM networks, wavelength conversion is an essential functionality to provide wavelength flexibility and avoid wavelength blocking. Using a 50 m long highly nonlinear photonic crystal fiber (HNL-PCF), with a simple four-wave mixing (FWM) scheme, wavelength conversion of single channel and multi-channel high-speed DPSK signals is presented. Wavelength conversion of an 80 Gbit/s RZ-DPSK-ASK signal generated by combining different modulation formats is also reported. Amplitude distortion accumulated over transmission spans will eventually be converted into nonlinear phase noise, and consequently degrade the performance of systems making use of RZ-DPSK format. All-optical signal regeneration avoiding O-E-O conversion is desired to improve signal quality in ultra long-haul transmission systems. Proof-of-principle numerical simulation results are provided, that suggest the amplitude regeneration capability based on FWM in a highly nonlinear fiber (HNLF). The first reported experimental demonstration of amplitude equalization of 40 Gbit/s RZ-DPSK signals using a 500 m long HNLF is presented. Using four possible phase levels to carry the information, DQPSK allows generation of high-speed optical signals at bit rate that is twice the operating speed of the electronics involved. Generation of an 80 Gbit/s DQPSK signal is demonstrated using 40 Gbit/s equipment. The first demonstration of wavelength conversion of such a high-speed signal is implemented using FWM in a 1 km long HNLF. No indication of error floor is observed. Using polarization multiplexing and combination of DQPSK with ASK and RZ pulse carving at a symbol rate of 40 Gbaud, a 240 Gbit/s RZ-DQPSK-ASK signal is generated and transmitted over 50 km fiber span with no power penalty. In summary, we show that direct detection and all-optical signal processing -including optical labeling, wavelength conversion and signal regeneration- that already have been studied intensively for signals using conventional on-off keying (OOK) format, can also be successfully implemented for high-speed phase modulated signals. The results obtained in this work are believed to enhance the feasibility of phase modulation in future ultra-high speed spectrally efficient optical communication systems

Modulation format comparison in PMD-Impaired 40Gbps systems

Tese de mestrado. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 200