Fiber-optic communication systems form the high-capacity transport infrastructure that enables global broadband data services and advanced Internet applications. The desire for higher per-fiber transport capacities and, at the same time, the drive for lower costs per end-to-end transmitted information bit has led to optically routed networks with high spectral efficiencies. Among other enabling technologies, advanced optical modulation formats have become key to the design of modern wavelength division multiplexed (WDM) fiber systems. In this paper, we review optical modulation formats in the broader context of optically routed WDM networks. We discuss the generation and detection of multigigabit/s intensity- and phase-modulated formats, and highlight their resilience to key impairments found in optical networking, such as optical amplifier noise, multipath interference, chromatic dispersion, polarization-mode dispersion, WDM crosstalk, concatenated optical filtering, and fiber nonlinearity

Advanced Optical Modulation Formats

The theoretical fundamentals of fiber-based optical parametric amplifiers(OPA) are reviewed,and their applications are discussed in this paper.In the end the future research aspects are expected.

Fiber-based Optical Parametric Amplifiers and Their Applications

A 1-Tb/s single-channel coherent optical OFDM (CO-OFDM) signal consisting of continuous 4,104 spectrally-overlapped subcarriers is generated using a novel device of recirculating frequency shifter (RFS) The RFS produces 3206-GHz wide spectrum using a single laser with superior flatness and tone-to-noise ratio (TNR) The 1-Tb/s CO-OFDM signal is comprised of 36 uncorrelated orthogonal bands achieved by adjusting the delay of the RFS to an integer number of OFDM symbol periods The 1- Tb/s CO-OFDM signal with a spectral efficiency of 33 bit/s/Hz is successfully received after transmission over 600-km SSMF fiber without either Raman amplification or dispersion compensation

1-Tb/s single-channel coherent optical OFDM transmission over 600-km SSMF fiber with subwavelength bandwidth access.

Silica-based highly nonlinear fibers (HNLFs) have been utilized as platforms for various applications, including fiber lasers, optical amplifiers, and optical signal processings. For the practical applications, nonlinearity enhancement without degrading the attenuation and tailoring the chromatic dispersions remain the key issues. Herein, we initially discuss the design of chromatic dispersions of HNLFs for desired applications. Then the fabrication results, including HNLFs with a longitudinally uniform zero-dispersion wavelength or with optimized higher order dispersion, are presented. Furthermore, using evolved HNLFs, we demonstrate a unique four-wave-mixing-based wavelength conversion. In addition, suppression of the stimulated Brillouin scattering, a critical issue for high-power applications, is discussed. We fabricate Al2O3-doped HNLF that has lower Brillouin gain by 6.1 dB as compared with that of conventional GeO 2-doped HNLF.

Silica-Based Highly Nonlinear Fibers and Their Application

Fast advancing silicon technology underpinned by Moore's law is creating a major transformation in optical fiber communications. The recent upsurge of interests in optical orthogonal frequency-division multiplexing (OFDM) as an efficient modulation and multiplexing scheme is merely a manifestation of this unmistakable trend. Since the formulation of the fundamental concept of OFDM by Chang in 1966 and many landmark works by others thereafter, OFDM has been triumphant in almost all the major RF communication standards. Nevertheless, its application to optical communications is rather nascent and its potential success in the optical domain remains an open question. This tutorial provides a review of optical OFDM slanted towards emerging optical fiber networks. The objective of the tutorial is two-fold: (i) to review OFDM fundamentals from its basic mathematical formation to its salient disadvantages and advantages, and (ii) to reveal the unique characteristics of the fiber optical channel and identify the challenges and opportunities in the application of optical OFDM.

OFDM for Flexible High-Speed Optical Networks

By combining the techniques of optical TDM with polarisation multiplexing and DQPSK modulation format, 240 km transmission of 1.28 Tbit/s and 160 km transmission of 2.56 Tbit/s has been performed in a single wavelength channel.

Single channel 1.28 Tbit/s and 2.56 Tbit/s DQPSK transmission

This paper reviews ultrahigh-speed data transmission in optical fibers based on optical time division multiplexing (OTDM) transmission technology. Optical signal processing in the transmitter and receiver as well as the requirements on ultrahigh-speed data transmission over a fiber link are discussed. Finally, results of several OTDM-transmission experiments, including 160-Gb/s transmission over 4320 km, 1.28-Tb/s transmission over 240 km, and 2.56-Tb/s transmission over 160-km fiber link, are described

Ultrahigh-Speed OTDM-Transmission Technology

By combining the techniques of optical TDM with polarization multiplexing and DQPSK modulation, we performed 240 km transmission of 1.28 Tbit/s and 160 km transmission of 2.56 Tbit/s in a single wavelength channel. (2 pages)

Clock recovery from a 160 Gbit/s data signal is demonstrated using a bidirectionally operated electroabsorption modulator (EAM) as phase comparator. Employing a differential detection scheme, excellent locking stability is achieved. The recovered clock signal allows error-free 160 Gbit/s transmission.

160 Gbit/s clock recovery with electro-optical PLL using bidirectionally operated electroabsorption modulator as phase comparator

The authors report an all-optical add-drop multiplexer based on gain-transparent operation of a semiconductor optical amplifier in a novel geometry. Error-free operation at 160 Gbit/s is demonstrated for all channels.

S. Ferber

Papers

Single channel 1.28 Tbit/s and 2.56 Tbit/s DQPSK transmission

Ultrahigh-Speed OTDM-Transmission Technology

Single channel 1.28 Tbit/s and 2.56 Tbit/s DQPSK transmission

160 Gbit/s clock recovery with electro-optical PLL using bidirectionally operated electroabsorption modulator as phase comparator

Error-free all-optical add-drop multiplexing at 160 Gbit/s