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.

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

We have generated a single-wavelength data signal with a data capacity of 5.1 Tbit/s. The enabling techniques to generate the data signal are optical time-division multiplexing up to a symbol rate of 1.28 Tbaud, differential quadrature phase shift keying as data format, and polarisation-multiplexing. For the first time, error-free performance with a bit error rate less than 10−9 is demonstrated for the 5.1 Tbit/s data signal. This is achieved in a back-to-back configuration using a direct detection receiver based on polarisation- and time-demultiplexing, delay-demodulation and balanced photo-detection.

Demonstration of 5.1 Tbit/s data capacity on a single-wavelength channel.

A 1-Tb/s single-channel coherent optical OFDM (CO-OFDM) signal consisting of continuous 4104 spectrally-overlapped subcarriers is generated using a recirculating frequency shifter (RFS). Theoretical and experimental analysis of the RFS is performed to study its effectiveness in extending OFDM bandwidth. In particular, the RFS produces a 320.6-GHz wide frequency comb from a single laser with superior flatness and tone-to-noise ratio (TNR). The 1-Tb/s CO-OFDM signal is consisted 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 3.3 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 With Orthogonal-Band Multiplexing and Subwavelength Bandwidth Access

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

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.

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

The optical sampling technique is a novel method to perform time-resolved measurements of optical data signals at high bit rates with a bandwidth that cannot be reached by conventional photodetectors and oscilloscopes. The chapter reviews the techniques that are used in optical sampling systems to perform the ultrafast sampling of the signal under investigation. In addition to the various nonlinear materials and effects used for the optical sampling gates and pulse sources, the realized optical sampling systems also differ in the way, in which the system is synchronized to the data signal. Systems have been reported using synchronous, random and software synchronized configurations. Applications of optical sampling systems include high bit rate waveform and eye diagram measurements, measurements of constellation diagrams of phase modulated data signals, time-resolved measurements of the state-of-polarization as well as investigations of fiber transmission impairments.

H.G. Weber

Papers

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

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

Optical sampling techniques