Nonlinear loop mirror-based all-optical signal processing in fiber-optic communications

All-optical data processing is expected to play a major role in future optical communications. The fiber nonlinear optical loop mirror (NOLM) is a valuable tool in optical signal processing applications. This paper presents an overview of our recent advances in developing NOLM-based all-optical processing techniques for application in fiber-optic communications. The use of in-line NOLMs as a general technique for all-optical passive 2R (reamplification, reshaping) regeneration of return-to-zero (RZ) on-off keyed signals in both high-speed, ultralong-distance transmission systems and terrestrial photonic networks is reviewed. In this context, a theoretical model enabling the description of the stable propagation of carrier pulses with periodic all-optical self-regeneration in fiber systems with in-line deployment of nonlinear optical devices is presented. A novel, simple pulse processing scheme using nonlinear broadening in normal dispersion fiber and loop mirror intensity filtering is described, and its employment is demonstrated as an optical decision element at a RZ receiver as well as an in-line device to realize a transmission technique of periodic all-optical RZ-nonreturn-to-zero-like format conversion. The important issue of phase-preserving regeneration of phase-encoded signals is also addressed by presenting a new design of NOLM based on distributed Raman amplification in the loop fiber. © 2008 Elsevier Inc. All rights reserved

DPSK regeneration: phase and amplitude noise suppression based on Kerr medium

The scope of this thesis is to identify and propose new schemes for Deferential Phase Shift Keying (DPSK) regeneration. DPSK modulation format presents increased robustness against ASE noise, which makes it strong candidate for use in long haul transmission systems. To achieve reasonable DPSK regeneration suppression of both the amplitude and phase noise is required. Three types of all-optical regenerators that make use of a Kerr medium, which can be a highly nonlinear fiber are analyzed. The first scheme is based on a modified nonlinear optical loop mirror (NOLM), with a subsequent addition of a bidirectional attenuator (DANOLM). The bidirectional attenuator allows to counterbalance the generation of the phase noise generated by the Gordon Mollenauer effect inside the Kerr medium. The second type of optical regenerator is based on the Self Phase Modulation (SPM) effect and offset filtering. Finally a novel scheme derived from the concepts of two former setups is presented and compared to the previous proposed. The operational conditions for optimum noise rejection are identified for each one of them. Through numerical simulations and detailed benchmarink we identify that our proposal outperforms all the schemes that have been presented previously in literature

All-optical pulse reshaping and retiming systems incorporating pulse shaping fiber Bragg grating

This paper demonstrates two optical pulse retiming and reshaping systems incorporating superstructured fiber Bragg gratings (SSFBGs) as pulse shaping elements. A rectangular switching window is implemented to avoid conversion of the timing jitter on the original data pulses into pulse amplitude noise at the output of a nonlinear optical switch. In a first configuration, the rectangular pulse generator is used at the (low power) data input to a nonlinear optical loop mirror (NOLM) to perform retiming of an incident noisy data signal using a clean local clock signal to control the switch. In a second configuration, the authors further amplify the data signal and use it to switch a (low power) clean local clock signal. The S-shaped nonlinear characteristic of the NOLM results in this instance in a reduction of both timing and amplitude jitter on the data signal. The underlying technologies required for the implementation of this technique are such that an upgrade of the scheme for the regeneration of ultrahigh bit rate signals at data rates in excess of 320 Gb/s should be achievable

DPSK regeneration: phase and amplitude noise suppression based on Kerr medium

The scope of this thesis is to identify and propose new schemes for Deferential Phase Shift Keying (DPSK) regeneration. DPSK modulation format presents increased robustness against ASE noise, which makes it strong candidate for use in long haul transmission systems. To achieve reasonable DPSK regeneration suppression of both the amplitude and phase noise is required. Three types of all-optical regenerators that make use of a Kerr medium, which can be a highly nonlinear fiber are analyzed. The first scheme is based on a modified nonlinear optical loop mirror (NOLM), with a subsequent addition of a bidirectional attenuator (DANOLM). The bidirectional attenuator allows to counterbalance the generation of the phase noise generated by the Gordon Mollenauer effect inside the Kerr medium. The second type of optical regenerator is based on the Self Phase Modulation (SPM) effect and offset filtering. Finally a novel scheme derived from the concepts of two former setups is presented and compared to the previous proposed. The operational conditions for optimum noise rejection are identified for each one of them. Through numerical simulations and detailed benchmarink we identify that our proposal outperforms all the schemes that have been presented previously in literature

An Optical Grooming Switch for High-Speed Traffic Aggregation in Time, Space and Wavelength

In this book a novel optical switch is designed, developed, and tested. The switch integrates optical switching, transparent traffic aggregation/grooming, and optical regener-ation. Innovative switch subsystems are developed that enable these functionalities, including all-optical OTDM-to-WDM converters. High capacity ring interconnection between metro-core rings, carrying 130 Gbit/s OTDM traffic, and metro-access rings carring 43 Gbit/s WDM traffic is experimentally demonstrated. The developed switch features flexibility in bandwidth provisioning, scalability to higher traffic volumes, and backward compatibility with existing network implementations in a future-proof way