M. Puleo

Performance assessment of a photonic ATM switch based on a wavelength-controlled fiber loop buffer

Summary form only given. We report the first BER measurement of a photonic switch based on a wavelength-controlled fiber loop buffer, in real operation, i.e., with computer-generated repeated random input traffic, with all interfering and noise sources. Further measurements will be carried out in the near future and compared to a simulation model, regarding the influence of wavelength crosstalks, number of circulations, and wavelength allocation.

Frequency stabilization of DFB laser diodes to the P(3) line of acetylene at 1.52688 μm by external phase modulation

The emission frequency of DFB laser diodes has been locked to the P(3) line of the roto- vibrational absorption spectrum of Acetylene at 1526.878 nm. An external phase modulator is used to obtain the error signal, thus resulting in absence of frequency modulation on the frequency stabilized output, as well as good short and long term stability. The stability has been evaluated analyzing the beat signal between two independently stabilized lasers.

Performance and limitations of laser diodes stabilized to the sides of molecular absorption lines of ammonia

Performance and limitations of laser frequency stabilization based on the locking to the side of an absorption line are discussed: experimental results of spectroscopic measurements and of the stabilization of 1543‐nm DFB laser diodes to ammonia absorption lines are presented.

Impact of DFB-LD FM response distortion, in amplitude and phase, on FSK coherent systems

The influence of amplitude and phase distortions of the FM response of DFB (distributed feedback) lasers on coherent FSK (frequency shift keying) transmission systems has been investigated. It was found that pattern effects are mainly due to phase distortions, while the IF (intermediate frequency) spectrum broadening is due to both amplitude and phase distortions. Possible remedies are described, including device selection, line coding, and phase and/or amplitude equalization of the FM response. A comparison between observed spectra and computer analysis has been performed, showing a good agreement. Transmission experiments at 140 Mb/s have been carried out, showing the predicted effects on the eye diagram.<<ETX>>

Laser frequency stabilization for high bit-rate FSK multichannel coherent systems

After reviewing some previously proposed laser frequency stabilization techniques for multichannel coherent systems, the authors present a simple, alternative method, making use of a scanning Fabry-Perot resonator. This technique, which proved effective in a preliminary experiment stabilizing a single DFB (distributed feedback) laser diode within less than 500 kHz, was successfully applied to the collective stabilization of a two-channel transmitter and can be easily extended to a multichannel configuration with a high number of channels. The same principle can operate, with some modification, in the presence of FSK (frequency shift keying) direct modulation. This has been experimentally demonstrated for a DFB laser that was directly modulated up to 2 Gb/s.<<ETX>>

Demonstration of polarisation independent coherent transmission by synchronous intra-bit polarisation spreading

Polarization-independent heterodyne detection of an FSK (frequency shift keying) signal has been demonstrated by the synchronous intrabit polarization spreading technique, which consists in the switching or proper modulation of the state of polarization of the laser output field inside the bit period. This approach is particularly suitable for distribution networks, as the polarization diversity function is shifted to the transmitter, thus resulting in a simpler and cheaper heterodyne receiver. A transmission experiment, making use of a 1.55 mu m DFB (distributed feedback) laser diode, directly FSK modulated at 155 Mb/s, a properly developed high-speed polarization modulator, and single filter heterodyne detection, has been successfully carried out. The penalty resulting from preliminary bit-error-rate measurements ranges from 4 to 6.5 dB, including the 3 dB intrinsic loss common to all polarization spreading techniques.<<ETX>>

A simple high sensitivity clock recovery circuit for 40-Gbit/s return to zero signals

Summary form only given. Summary form only given. An all-optical optical time-division multiplexing-wavelength-division multiplexing (OTDM-WDM) interface, aimed at a capacity of 40 Gbit/s, under development in the frame of the ACTS project OPEN, realizes the conversion of an OTDM data stream into four WDM data streams, exploiting an MZI-SOA device simultaneously performing demultiplexing and wavelength conversion. The operation of this converter requires four pulsed signals at different wavelengths and at 10 GHz repetition rate, properly synchronized so that each pulse corresponds to a different bit of the incoming data stream. To achieve this synchronization, a clock recovery circuit, whose structure is reported, has been realized. The clock component at 40 GHz of the incoming RZ signal is detected by a narrow-band photoreceiver, featuring 78 dB/spl Omega/ transimpedance gain and 37 pA/spl radic/Hz noise around 40 GHz, based on a side-illuminated AlGaInAs-InP PIN diode followed by a GaAs PHEMT MMIC.

Photonics applications in switching: An ATM optical node

Abstract An ATM optical node architecture that carries out cell routing and buffering by photonic means, controlled by electronic circuits, is presented. An evolutionary approach, where cell aggregation and compression are introduced to achieve a large throughput, with a high performance, is also described. And we report experimental results that demonstrate the feasibility of all the relevant photonic functions, based on advanced optoelectronic devices, namely: fast wavelength reassignment, suitable for multigigabit operation, based on fast tunable lasers and semiconductor optical amplifiers; high bit rate packet storage in a multiwavelength fiber loop memory including fast optical gates; dynamic wavelength selection, based on distributed feedback (DFB) filters with nanosecond tuning response; and all optical demultiplexing of multigigabit/s time division multiplexing (TDM) signals by means of saturated semiconductor optical amplifiers.

Modal dependence of chromatic dispersion in optical fibers

Chromatic dispersion in optical fibers is a result of material and waveguide effects. In graded-index fibers there could be a contribution from nonlinear dispersive properties of the core material, although it has been claimed that such an effect is negligible.1 All these factors affect each mode in a different way. Therefore, determination of the wavelength of zero material dispersion (ZMD) is dependent on the propagating mode volume with practical impact on system design. Measurement of chromatic dispersion properties of different modes can in principle give some information about these problems. In this paper we show results of chromatic dispersion measurements performed by selectively exciting different groups of mode.

Characterization Of Laser Diode Intensity Noise At Microwave Frequencies With High Sensitivity

A measurement technique has been developed, that allows the accurate characterization of laser diode intensity noise up to microwave frequencies, with high sensitivity. Relative intensity noise levels lower than 10-15 Hz-1 can be measured, with good accuracy, up to 10 GHz. Several examples are presented, showing the effects of reflections on laser noise.