All-optical multiwavelength clock recovery using integratedsemiconductor amplifier array module

Simultaneous all-optical clock-recovery of WDM channels at 10 Gbit/s is demonstrated in an actively-modelocked fibre ring laser configuration using a novel 22-channel semiconductor optical amplifier array module integrated with two waveguide grating routers. The technique is based on using adjacent free-spectral ranges for the incoming data and recovered clock     

Performance of All-Optical Multicasting Via Dual-Stage XGM in SOA for Grid Networking

The letter presents a study on the performance of an all-optical multicasting technique utilizing the nonlinearity of semiconductor optical amplifier (SOA) technology for all-optical grid computing network. The technique not only has the capability to optically control the degree of multicasting but also performs all-optical switching simultaneously. Experimental results show the design's capability to multicast an incoming 10-Gb/s optical signal onto 16 outgoing signals using cross-gain modulation in a single SOA. A second SOA is also included in the design as a 2R regenerator     

Optical tank circuits used for all-optical timing recovery

A novel all-optical timing-recovery scheme that uses an optical tank circuit is presented. An optical clock synchronized to an incoming data stream is generated by extracting line spectral components in the incoming data stream using an optical resonator whose free spectral range is equal to the incoming data bit rate. The principle of operation is demonstrated using a confocal Fabry-Perot-type optical tank circuit and a fiber-ring-type optical tank circuit at 2 Gb/s and 324 Mb/s, respectively. Quality factor in the baseband domain is measured and shown to agree well with the theoretical value. A workable data bit rate, required source linewidth, and stability are discussed     

All-optical clock recovery from 2.5 Gbit/s NRZ data using selfpulsating 1.58 mu m laser diode

For the first time, all-optical clock extraction from 2.5 Gbit/s NRZ data is demonstrated using a two contact InGaAsP semiconductor selfpulsating laser diode (SP-LD) for what the authors believe to be the first time. The saturable absorber region of the device was doped with Zn ions to reduce the carrier lifetime such that strong selfpulsations at frequencies up to 4 GHz were obtained. Injection of a 10 mu W optical data signal at a wavelength approximately 15 nm lower than the lasing wavelength was sufficient to synchronise the selfpulsations to the incoming NRZ data stream. Similar effects were seen for RZ formated data. Such all-optical clock extraction techniques will find application in future multigigabit per second optical networks and for OEIC applications.<>     

All-Optical 3R Burst-Mode Reception at 40 Gb/s Using Four Integrated MZI Switches

We demonstrate an all-optical retime, reshape, reamplify (3R) burst-mode receiver (BMR) operating error-free with a 40-Gb/s variable-length asynchronous optical data packets that exhibit up to 9-dB packet-to-packet power variation. The circuit is completely based upon hybrid integrated Mach-Zehnder interferometric (MZI) switches as it employs four cascaded MZIs, each one performing a different functionality. The 3R burst-mode reception is achieved with the combination of two discrete all-optical subsystems. A reshape, reamplify BMR employing a single MZI is used first to perform power equalization of the incoming bursts and provide error-free data reception. This novel approach is experimentally demonstrated to operate error-free, even for a 9-dB dynamic range of power variation between bursty data packets and for a wide range of average input power. The obtained power-equalized data packets are then fed into a 3R regenerator to improve the signal quality by reducing the phase and amplitude jitter of the incoming data. This packet-mode 3R regenerator employs three MZIs that perform wavelength conversion, clock extraction, and data regeneration for every packet separately and operates at 40 Gb/s, exhibiting rms timing jitter reduction from 4 ps at the input to 1 ps at the output and a power penalty improvement of 2.5 dB     

Optical 40-gb/s 3R regenerator with a combination of the SPM and XAM effects for all-optical networks

An all-optical 3R regenerator with a combination of self-phase modulation (SPM) and cross-absorption modulation (XAM) effects is proposed and investigated. Principle performances of the proposed all-optical 3R regenerator were experimentally investigated at a signal bit rate of 40 Gb/s. The all-optical 3R regenerator, which is located at the midpoint of a 1080-km transmission line, successfully provided an approximately 3-dB improvement of the Q-factor both just after regeneration and after totally 1080-km transmission. The chromatic dispersion tolerance of the proposed 3R regenerator was also investigated and successfully enhanced to about twice as wide by introducing a predistortion block configuration including a highly nonlinear fiber (HNLF). It was confirmed that the proposed all-optical 3R regenerator can become one of the strong candidates for the actual deployment of the all-optical network.     

Self-Clocked All-Optical Add/Drop Multiplexer for Asynchronous CDMA Ring Networks

In this paper, we demonstrate a novel self-clocked code-drop unit for incoherent optical code-division multiple-access (CDMA) networks. The unit is based on an all-optical thresholder with internal wavelength conversion that creates a control signal for the drop gate from the incoming data stream. This architecture does not require an external clock signal for drop operation and can be used in asynchronous ring networks. The proposed unit is experimentally demonstrated for two-dimensional time-wavelength optical CDMA codes at a bit rate of 2.5 Gbit/s with two different types of drop gates: terahertz optical asymmetric multiplexer and nonlinear fiber-based loop mirror. Error-free operation is achieved in both configurations. The development of a self-clocked add/drop multiplexer demonstrates a novel concept of asynchronous node operation in multiple access networks.      

All-Optical Label Swapping Using Bistable Semiconductor Ring Laser in an Optical Switching Node

This paper demonstrates an optical node that simultaneous carries out multicast optical switching and all-optical label swapping. While the optical payload is being forwarded by a fast optical switch matrix, the optical label is processed by a semiconductor ring laser (SRL) bistable. Old address bits in the label are erased by optically blocking the switching of the ring laser and new address bits are inserted by modulating the output from SRL directly. This label swapping scheme is the first demonstration of bit-level data processing using the all-optical logic capabilities of a semiconductor ring laser.     

All-optical regenerator

An all-optical regenerator has been demonstrated using two self-electro-optic effect devices (SEED) and a local pump laser. The regenerator's optical signal processing included clock recovery, data retiming and signal amplification. A 2 dB optical gain was attained at a 5 kbit/s data rate     

40 Gbit/s all-optical clock recovery using two-section gain-coupledDFB laser and semiconductor optical amplifier

40 Gbit/s wavelength and polarisation insensitive all-optical clock recovery using a two-section distributed feedback (DFB) laser has been demonstrated. The polarisation sensitivity of the two-section DFB laser was solved by converting incoming data onto a local laser through cross-gain modulation using a semiconductor optical amplifier. The scheme has a sensitivity of -13 dBm     

Very-high-speed fibre-optic networks for broadband communications

Single-mode optical fibres have an enormous transmission bandwidth which can support ultra-high-speed digital transmission and networking. The use of electrical signal-processing, however, ultimately limits the network capacity. To eliminate the throughput bottleneck, all-optical processing techniques should be employed in a fibre-optic network. This paper discusses several schemes for implementing optical time division multiple access (OTDMA) networks with the emphasis on optical clock distribution, synchronisation and all-optical detection. The use of a fast-switching bistable laser diode as an all-optical threshold detector and data regenerator is suggested. A dual-wavelength OTDMA technique is investigated, which can be used for digital TV or future HDTV distributions. Moreover, an efficient multiple access scheme, called wavelength division multiple access with optical time division multiplexing (WDMA-OTDM), is proposed for broadband communication services. It is shown that WDMA-OTDM has all the advantages possessed by the individual OTDMA and WDMA schemes but offers improved flexibility and capacity     

Cascadability of an All-Optical 3R Regenerator Utilizing Nonlinear Phase Modulation and Offset Filtering at 10 and 40 Gb/s

The cascadability of a polarization-insensitive wavelength-preserving all-optical 3R regenerator is experimentally investigated for bit rates of 10 and 40 Gb/s. The regenerator consists of a self-pulsating laser for clock recovery, cross-phase-modulation-based retiming, and self-phase-modulation-based reshaping. A recirculating loop is used to demonstrate the cascadability of the regeneration scheme by transmitting return-to-zero on–off-keyed signals over 18 000 km at 10 Gb/s and over 8000 km at 40 Gb/s.      

1.3-$mu$m Amplifier-Free All-Optical 2R Regenerator Using Two-Mode Injection-Locked Distributed Feedback Laser Diode

This study presents a novel and cost-effective 1.3-mum all-optical 2R regenerator based on a two-mode injection-locked distributed feedback laser diode. The proposed 2R regenerator, with 14.13-dB small signal gain, has achieved an amplifier-free 10-Gb/s straight line transmission over 60 km while keeping the power penalty less than 0.84 dB at bit-error rate (BER) =10^-9. In addition, properties like BER degradation, output extinction ratio, gain, and data-rate transparency are also experimentally investigated     

All-optical timing extraction using an optical tank circuit

An ultrafast all-optical timing extraction method using an optical tank circuit is described, and experimental results at 2 Gb/s are reported. A Fabry-Perot resonator, whose free spectral range is equal to the clock frequency of the incoming optical data stream, is utilized as the optical tank circuit. Its fully passive structure and ultra-high-bit-rate operation (~Tb/s) is possible through decreasing resonator length     

A study on the wavelength conversion and all-optical 3R regeneration using cross-absorption modulation in a bulk electroabsorption modulator

A 40-Gb/s 3R regenerator with a two-ring injection mode-locked fiber laser as the clock recovery and an electroabsorption modulator (EAM) as the reshaping optical decision gate is proposed and demonstrated. The cross-absorption modulation effect in a bulk EAM was also numerically modeled. Using this model, both the shape and the extinction ratio of the optical decision gate are optimized. The model is also employed to investigate the tolerance of the timing jitter, the chromatic dispersion, and the polarization mode dispersion of an all-optical 3R regenerator based on a bulk EAM decision gate. The operation margin of the 3R regenerator is presented. The theoretical results agree well with the experimental results.     

A Fiber-Based All-Optical 3R Regenerator for DPSK Signals

Analysis of an all-optical 3R regenerator for differential phase-shift keying (DPSK) signals is presented. Incoming DPSK signals impaired by noise are first demodulated to on-off keying (OOK) signals by a delay interferometer. The amplitude of the OOK signals is then stabilized by a fiber-based all-optical 2R regenerator. In a subsequent nonlinear fiber, locally generated optical clock pulses are phase-modulated by the stabilized OOK pulses and are output as regenerated signals. It is shown that significant phase-noise suppression is achieved by strong amplitude regeneration     

An all-optical 2R regenerator using a compact self-seeded Fabry-Pe/spl acute/rot laser diode incorporated in a bidirectional EDFA

An all-optical 2R regenerator, based on a compact self-seeded Fabry-Pe/spl acute/rot laser diode with a 10-mm-long embedded fiber Bragg grating cavity, and a bidirectional erbium-doped fiber amplifier, is proposed and experimentally demonstrated to execute all-optical 2R regeneration at 10 Gb/s. Compared with the conventional 1R regeneration, the proposed scheme has achieved significant 6.4-dB improvement of power penalty at bit-error ratio =10/sup -9/ in the transmission experiment over 100-km standard single-mode fiber.     

All-optical 2R regeneration based on a compact self-seeded fabry-Pe/spl acute/rot laser diode with an embedded fiber Bragg grating

A cost-effective method, based on the injection-locking technique of a compact self-seeded Fabry-Pe/spl acute/rot laser diode with a 10-mm-long embedded fiber Bragg grating cavity, is proposed and experimentally compared with the two-mode injection-locked scheme for all-optical 2R regeneration at 10 Gb/s. Placing the presented all-optical 2R regenerator after a 50-km fiber significantly improves the transmission performance of a signal over 50- and 100-km fiber links. The power penalties at BER=10/sup -9/ are similar to those of the two-mode injection-locked scheme.     

Noise Tolerance Assessment and System Design Discussion of a Saturable-Absorption-Based All-Optical 2R Regenerator

This letter presents the cascadability assessment and the noise tolerance characterization of an all-optical 2R regenerator based on saturable absorption and nonlinear effects in fiber. The impact of optical signal-to-noise ratio on the 2R regenerator performance is shown, and a regenerator characterization technique that can be used for system design and engineering is discussed.     

Cascaded Operation of a 2R Burst-Mode Regenerator for Optical Burst Switching Network Transmission

We demonstrate the cascaded operation of an all-optical 2R burst-mode regenerator consisting of a single Mach-Zehnder interferometer, using a loop configuration that introduces a 6-dB power variation on each recirculation of the data. The device is shown to regenerate error-free 10-Gb/s data streams for up to six successive loop recirculations.