Error-free all-optical wavelength conversion at 168 Gb/s, which is the highest repetition rate ever reported, has been achieved by using a symmetric-Mach-Zehnder (SMZ)-type switch. Low-power-penalty 84-Gb/s operation is also demonstrated. The push-pull switching mechanism of the SMZ switch enables such ultrafast operation based on cross-phase modulation associated with the carrier depletion in a semiconductor optical amplifier. The configuration of the delayed-interference signal-wavelength converter, which is a simplified variant of the SMZ switch, is used in this experiment.

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168-Gb/s all-optical wavelength conversion with a symmetric-Mach-Zehnder-type switch

Future bandwidth demand in optical communication and signal processing systems will soon exceed 100?Gb?s?1 as is commonly forecasted from a throughput experience curve for communication systems. However, such systems cannot be realized without introducing ultrafast, all-optical devices, since existing optoelectronic and electronic devices and integrated circuits would not be able to function at a bit rate exceeding 100?Gb?s?1, because of the speed limit intrinsic to conventional semiconductor materials and devices. All-optical devices based on completely new principles, not being restricted by properties of existing materials and device principles, must be developed for the realization of ultrafast communication and signal processing systems. This paper reviews requirements of ultrafast all-optical devices and recent progress in ultrafast light sources and all-optical switches based on either novel device principles or ultrafast phenomena in novel materials such as quantum-confined nanostructures. Recent developments described here include mode-locked lasers and a variety of all-optical switches based on different phenomena including Mach?Zehnder interferometer structures, spin relaxation, intersubband transition, and ultrafast absorption recovery in organic thin films and semiconductor quantum dots. Some of the recent developments have already shown capability of basic functions such as ultrafast pulse generation and signal processing at the bit rate of 500?Gb?s?1 to 1?Tb?s?1. Technical challenges expected for the future are discussed in view of their applications in real systems.

https://iopscience.iop.org/article/10.1088/1367-2630/6/1/183/pdf

Femtosecond all-optical devices for ultrafast communication and signal processing

In a semiconductor optical amplifier (SOA) with copropagating optical pump pulses, the application of a nonlinear phase shift to optical signals provides the driving force for all-optical interferometric switching. We study, both analytically and experimentally, the dependencies of the nonlinear phase shift on the driving frequency (42–168 GHz) and on the SOA parameters. We have found that the nonlinear phase shift (ΔΦNL) decreases with the driving frequency but that this decrease is only linear, i.e., ΔΦNL∝f-1. We have also found that the nonlinear phase shift in the SOA linearly increases with the injection current (Iop), i.e., ΔΦNL∝Iop, even in this ultrahigh-frequency range.

http://www.ultrafast.ee.uec.ac.jp/pubs/ueno-phaseshifts-josab2002.pdf

Nonlinear phase shifts induced by semiconductor optical amplifiers with control pulses at repetition frequencies in the 40–160-GHz range for use in ultrahigh-speed all-optical signal processing

Publisher Summary The pseudo–linear transmission is a method for the transmission of high-speed time-division multiplexed (TDM) signals where fast variations of each channel waveform with cumulative dispersion allows important averaging of the intrachannel effects of fiber nonlinearity. The pseudo–linear transmission involves complex optimization of modulation format, dispersion mapping, and nonlinearity. These transmissions occupy a space somewhere between dispersion-mapped linear transmission and nonlinear soliton transmission. The pseudo-linear regime of transmission is characterized by a rapid pulse broadening, which results in a dramatic reduction of the solitonic effect on each pulse. As a result, full dispersion compensation can be used in this regime. Extensive analysis of pseudo-linear transmission and reviews of the TDM transmission experiments at 40 and 160 Gb/s have been provided in the chapter. Two new forms of nonlinear interactions between rapidly dispersing pulses namely intrachannel cross–phase modulation (IXPM) and intrachannel four–wave mixing (IFWM) are also presented. These two intrachannel effects are the most important nonlinear interactions in pseudo-linear transmission and determine the dispersion mapping even for the wavelength–division multiplexed (WDM) systems. Further, the chapter describes the semiconductor–based technologies that enable the development of stable and reliable high–speed transmitters and receivers.

Pseudo-Linear Transmission of High-Speed TDM Signals: 40 and 160 Gb/s

Penalty-free data-pulse regeneration at 84 Gb/s was achieved down to an error rate level of 1/spl times/10/sup -11/ by using a data pattern length of 2/sup 31/-1. A symmetric-Mach-Zehnder-type all-optical polarization-insensitive semiconductor regenerator was used.

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Penalty-free error-free all-optical data pulse regeneration at 84 Gb/s by using a symmetric-Mach-Zehnder-type semiconductor regenerator

We have developed a hybrid-integrated symmetric Mach-Zehnder all-optical switch and evaluated the demultiplexing of 168-Gb/s data pulses at a repetition rate of 10 GHz with this switch. A compact, stable device was realized by assembling semiconductor optical amplifiers as nonlinear waveguides on a planar lightwave circuit in a self-aligned manner. A 6.0-ps switching window needed for 168-Gb/s demultiplexing was provided by the push-pull operation of the symmetric Mach-Zehnder all-optical switch. Demultiplexed signal light showed a high extinction ratio of better than 18 dB. Error-free demultiplexing with a bit error rate of 10/sup -11/ was achieved.

Demultiplexing of 168-Gb/s data pulses with a hybrid-integrated symmetric Mach-Zehnder all-optical switch

A hybrid integrated symmetric Mach-Zehnder (HI-SMZ) all-optical switch is reported. It has a very high dynamic extinction ratio of >20 dB at a switching speed of <4 ps. No delay was found in its rise and fall times with 1 ps control pulses. Thus, the HI-SMZ all-optical switch is capable of high extinction, quasi-square-like modulation up to a speed of /spl sim/4 ps, corresponding to a bit rate exceeding 200 Gbit/s.

Hybrid integrated symmetric Mach-Zehnder all-optical switch with ultrafast, high extinction switching

The symmetric Mach-Zehnder (SMZ) all-optical switch is quite promising for various types of future high-speed all-optical processing. We have developed a hybrid-integrated SMZ all-optical switch and achieved the error-free demultiplexing of 168 Gbps data pulses.

168 Gbps error-free demultiplexing with hybrid-integrated symmetric Mach-Zehnder all-optical switch

A newly developed hybrid-integrated Symmetric Mach-Zehnder (HI-SMZ) all-optical switch is reported. For integration, we chose the Symmetric Mach-Zehnder (SMZ) structure rather than the Polarization-Discriminating Symmetric Mach-Zehnder (PD-SMZ) structure which is similar to SMZ but more often used in experiments using discrete optical components. We discuss advantages and disadvantages of SMZ and PD-SMZ to show that SMZ is more suitable for integration. We also discuss about the use of SOAs as nonlinear elements for all-optical switches. We conclude that, although the ultrafast switching capability of SMZ is limited by the gain compression of SOAs, the very low switching energy is more important for practical devices. We then describe the HI-SMZ all-optical switch. This integration scheme has advantages which include low loss, low dispersion silica waveguides for high speed operation and ease in large scale integration of many SMZs with other optical, electrical, and opto-electrical devices. We show that a very high dynamic extinction ratio is possible with HI-SMZ. We also examine HI-SMZ with 1 ps pulses to show its ultrafast capability. Finally, we describe a 168 to 10.5Gbps error-free demultiplexing experiment which is to our best knowledge the fastest experiment with an integrated device. key words: all-optical switch, nonlinear optics, optical commu-

Takara Sugimoto

Papers

Demultiplexing of 168-Gb/s data pulses with a hybrid-integrated symmetric Mach-Zehnder all-optical switch

Hybrid integrated symmetric Mach-Zehnder all-optical switch with ultrafast, high extinction switching

168 Gbps error-free demultiplexing with hybrid-integrated symmetric Mach-Zehnder all-optical switch

Ultrafast Hybrid-Integrated Symmetric Mach-Zehnder All-Optical Switch and Its 168 Gbps Error-Free Demultiplexing Operation

Hybrid Integrated 8-Channel SOAG Receptacle Module with Driver Circuits