<title>Optical subcarrier multiplexing for multigigabit optical communication</title>

Abstract

Future broadband fiber communication networks for commercial and/or military application will require tens to hundreds of communication channels, each channel transporting multigigabit data resulting in an aggregate throughput upwards of 100 Gb/s. Optical-based systems have the potential for realizing such networks because of the inherent speed of optical signals, and the large optical (30-terahertz) bandwidth that can be exploited for communication. Optical signal multiplexing in the spectral and temporal domains provides means of interconnecting and transporting large user data through a network. One approach to achieving multigigabit data transport via time division multiplexed requires the development of femtosecond mode-locked lasers or soliton lasers of high repetition rates. Such lasers are bulky making them impractical for systems applications. Furthermore their performance can be severely affected by optical nonlinearities. WDM offers another approach to multigigabit data transport. Typically WDM systems utilize a separate single frequency laser for each channel. Stabilizing and controlling each individual wavelength of a high density WDM system is difficult and costly. Furthermore cross-talk and cross-phase modulation limit the channel capacity in WDM systems. In this paper we propose a subcarrier multiplexing scheme as an alternative to multigigabit fiber optics data communication. In this approach, a comb of optical RF subcarriers are generated in a matched-pair of optical traveling-wave amplifiers (TWA). Each subcarrier serves as a transmission channel. The most important aspect of this approach is that optical processing of the subcarriers are done via the main optical carrier. Thus amplification of the main carrier translates into a direct amplification of the subcarriers. We present theoretical framework and simulation results for optical RF subcarrier generation.