Recent advances in developing nonlinear optical techniques for processing serial digital information at high speed are reviewed. The field has been transformed by the advent of semiconductor nonlinear devices capable of operation at 100 gigabits per second and higher, well beyond the current speed limits of commercial electronics. These devices are expected to become important in future high-capacity communications networks by allowing digital regeneration and other processing functions to be performed on data signals “on the fly” in the optical domain.

https://science.sciencemag.org/content/sci/286/5444/1523.full.pdf

Nonlinear Optics for High-Speed Digital Information Processing.

Since the first deployments of fiber-optic com- munication systems three decades ago, the capacity carried by a single-mode optical fiber has increased by a staggering 10 000 times. Most of the growth occurred in the first two decades with growth slowing to ten times in the last decade. Over the same three decades, network traffic has increased by a much smaller factor of 100, but with most of the growth occurring in the last few years, when data started dominating network traffic. At the current growth rate, the next factor of 100 in network traffic growth will occur within a decade. The large difference in growth rates between the delivered fiber capacity and the traffic demand is expected to create a capacity shortage within a decade. The first part of the paper recounts the history of traffic and capacity growth and extrapolations for the future. The second part looks into the technological chal- lenges of growing the capacity of single-mode fibers by pre- senting a capacity limit estimate of standard and advanced single-mode optical fibers. The third part presents elementary capacity considerations for transmission over multiple trans- mission modes and how it compares to a single-mode trans- mission. Finally, the last part of the paper discusses fibers supporting multiple spatial modes, including multimode and multicore fibers, and the role of digital processing techniques. Spatial multiplexing in fibers is expected to enable system capacity growth to match traffic growth in the next decades.

https://www.icg.isy.liu.se/courses/optical/Capacity_Trends.pdf

Capacity Trends and Limits of Optical Communication Networks Discussed in this paper are: optical communication network traffic evolution trends, required capacity and challenges to reaching it, and basic limits to capacity.

A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

WDM optical network with passive pass-through at each node

1. Introduction: Building a City of Light 2. Guiding Light and Luminous Fountains (1841-1890) 3. Fibers of Glass 4. The Quest for Remote Viewing: Television and the Legacy of Sword Swallowers (1895-1940) 5. A Critical Insight: The Birth of the Clad Optical Fiber (1950-1955) 6. 99 Percent Perspiration: The Birth of an Industry (1954-1960) 7. A Vision of the Future: Communicating with Light (1880-1960) 8. The Laser Stimulates the Emission of New Ideas (1960-1969) 9. "The Only Thing Left Is Optical Fibers" (1960-1969) 10. Trying to Sell a Dream (1965-1970) 11. Breakthrough: The Clearest Glass in the World (1966-1972) 12. Recipes for Grains of Salt: The Semiconductor Laser (1962-1977) 13. A Demonstration for the Queen (1970-1975) 14. Three Generations in Five Years (1975-1983) 15. Submarine Cables: Covering the Ocean Floor with Glass (1970-1995) 16. The Last Mile: An Elusive Vision 17. Reflections on the City of Light Appendix A. Dramatis Personae: Cast of Characters Appendix B. A Fiber-Optic Chronology

City of Light: The Story of Fiber Optics

Recent progress in optical time-division-multiplexed (TDM) transmission technologies is reviewed including optical short pulse generation, time-division multiplexing/demultiplexing, timing extraction, and waveform measurement. The latest 400-Gbit/s transmission experiments based on optical signal processing are presented and the possibility of terabit/second TDM transmission is discussed.

Ultrahigh-speed optical time-division-multiplexed transmission technology based on optical signal processing

This paper investigates experimentally and theoretically the signal-to-noise ratio (SNR) characteristics of 100 Gb/s all-optical demultiplexing using a nonlinear optical loop mirror (NOLM). The analysis takes into account two effects that degrade the SNR associated with NOLM demultiplexing. First is channel crosstalk originating from the leakage of nontarget channels. Second is the intensity fluctuations of demultiplexed signals caused by the combined effects of timing jitter and a profile of the switching window. Considering these two effects, power penalties associated with NOLM. Demultiplexing are theoretically evaluated using the conventional noise theory of an optical receiver followed by an optical preamplifier. Experimental results of bit error rate measurements for 100 Gb/s demultiplexing using three different NOLMs with different intrinsic crosstalk values, defined by signal transmittance in the absence of control pulses, show that the power penalties are in good agreement with the evaluation based upon our proposed analysis. It can be found from our investigation in demultiplexing from 100 to 10 Gb/s that intrinsic crosstalk of less than -25 dB, corresponding to a coupling ratio, K, of |K-0.5|/spl les/0.03, is required for the power penalty of less than 1 dB. The root-mean-square (rms) value of the relative timing jitter necessary for obtaining a sufficient timing tolerance width for combining control and signal pulses is determined.

Signal-to-noise ratio analysis of 100 Gb/s demultiplexing using nonlinear optical loop mirror

To construct large-capacity flexible optical networks, utilization of both optical time-division multiplexing (OTDM) [1] and wavelength-division multiplexing (WDM) technologies [2], [3] will be of vital importance, in which broadband low-noise optical sources are expected to play a major role.

100 Gbit/s x 10 channel OTDM/WDM Transmission using a Single Supercontinuum WDM Source

We present a successful demonstration of ultra-fast all-optical time-division demultiplexing with simultaneous multiple-channel output, a vital function for all-optical demultiplexers. The demultiplexing operation is based on multichannel four-wave mixing (FWM) in a semiconductor optical amplifier. Error-free, simultaneous live-channel-output, 100-6.3-Gb/s demultiplexing is successfully performed.

100-Gb/s multiple-channel output all-optical OTDM demultiplexing using multichannel four-wave mixing in a semiconductor optical amplifier

An all-optical polarization independent optical time division multiplexer and demultiplexer which are stable as well as very fast, while being independent of the polarization state of the input optical signal pulses. The demultiplexer has a wavelength-division-multiplexing coupler for wavelength-division-multiplexing time-division-multiplexed optical signal pulses and optical control pulses, and splitting the optical signal pulses at a splitting ratio of 1:1 into two ports, the optical control pulses being in a polarization state in which two orthogonally polarized components have a substantially identical amplitude; an optical Kerr medium with birefringence, for connecting two ports of the wavelength-division-multiplexing coupler, the optical Kerr medium incorporating a birefringence compensation mechanism for compensating a polarization dispersion between two principal axes of the birefringence; and a wavelength division demultiplexer for wavelength-division-demultiplexing time-wise overlapping optical signal pulses and optical control pulses propagated through the optical Kerr medium, to obtain time-division-demultiplexed optical signal pulses. In the multiplexer, the input and output relationship is reversed in the same configuration.

All-optical polarization independent optical time division multiplexer and demultiplexer with birefringence compensation

Several kinds of new optical technology are now being developed for extremely high bit-rate optical transmission systems. The nonlinear optical loop mirror (NOLM) has been used as a very high-speed demultiplexer [l]-[3]. A timing extraction phase lock loop (PLL) using traveling-wave laser-diode amplifier (TW-LDA) [4] and a mode-locked Er-doped fiber ring laser (MLRL) [5] have also been developed.

Kentaro Uchiyama

Papers

Signal-to-noise ratio analysis of 100 Gb/s demultiplexing using nonlinear optical loop mirror

100 Gbit/s x 10 channel OTDM/WDM Transmission using a Single Supercontinuum WDM Source

100-Gb/s multiple-channel output all-optical OTDM demultiplexing using multichannel four-wave mixing in a semiconductor optical amplifier

All-optical polarization independent optical time division multiplexer and demultiplexer with birefringence compensation

100 Gbit/s, 50 km Optical Transmission Employing All-Optical Multi/Demultiplexing and PLL Timing Extraction