At&t Bell Laboratories

American Telephone & Telegraph Co., At&t Bell Laboratories

American Telephone and Telegraph, Co.

Nils A Olsson

Charles H Henry

Rudolf F Kazarinov

Won-Tien Tsang

Kenneth J Orlowsky

Greg E Blonder

Rodney C Alferness

Chandra K Patel

Liang D Tzeng

Yan-Chi Shi

Melvyn Dixon

Anne I Lidgard

Govind P Agrawal

M T Fatehi

Robert E Tench

In this invention telemetry information is transmitted in an optical fiber communication system by providing an amplifier pump with excess power beyond that necessary to pump the amplifier. The excess power is not used to pump the amplifier but is rather used to transmit the telemetry information. In a specific embodiment, an optical communication system including a doped optical fiber amplifier such as, for example, an erbium doped amplifier, is provided with an amplifier pump which operates at approximately 1.48 .mu.m. The amplifier pump is provided with excess power so as to transmit telemetry information. In a specific embodiment, the telemetry signal can be detected with a low cost photodetector at a subsequent station.

Telemetry for optical fiber amplifier repeater

In an optical communication system, in order to reduce simultaneously both second and third harmonic distortion in a light beam from a modulated semiconductor laser, a nonlinear interferometric deivce--such as a Fabry-Perot etalon--is inserted in the path of the beam. The parameters of the interferometric device--such as its phase and finesse--are selected such that, for a suitable laser bias current, the second and third harmonics produced by nonlinearities of the laser (plus nonlinearities of the transmission medium such as an optical fiber, if any, through which the beam propagates from source to receiver) are significantly compensated by nonlinearities of the interometric device.

Interferometric devices for reducing harmonic distortions in laser

The span of an optical dispersion-limited fiber for propagating optical pulses is improved by simultaneously chirping and amplifying the stream by means of a saturated semiconductor laser amplifier. The chirp causes a compression of the pulses as they propagate through an initial portion of the fiber, whereby the span of the fiber is increased.

Saturated semiconductor laser amplifier for compensation of optical

In a fiber-optic communication system, a polarization independent semiconductor optical amplifier structure is achieved by tailoring the height-width aspect ratio of its active region to a value at least close to unity and at the same time using a laser cavity structure in which the end mirrors are buried in the semiconductor body in which the optical amplifier structure is built.

Polarization independent semiconductor optical amplifier

A single frequency lightwave system employs semiconductor, optical amplifiers arranged in tandem with suitable nose filtering and isolation between amplifier stages. Feedback control maintains overlap between the signal frequency and one of the passbands of the amplifiers. Either direct detection or coherent detection can be used. Also described is a receiver front end which includes such an amplifier between the incoming signal and a photodetector. Both transmission systems and switching systems are described.

Lightwave systems using optical amplifiers

A polarization independent semiconductor amplifier is used in a double-pass configuration; that is, the output of the amplifier is passed through a 45.degree. Faraday rotator to a mirror and then through the rotator and the amplifier again. Polarization independent gain is thus achieved.

Polarization independent optical amplifier apparatus

In the interest of ease of manufacture, hybrid lasers of distributed-Bragg-reflector type are preferred for use as light sources in optical communications. Such lasers are made to operate away from mode instabilities by adjusting a laser parameter such as, e.g., laser temperature, thereby assuring highly error-free transmission. Alternatively, by suitable design of the Bragg reflector it is possible to render mode instability of negligible influence on error rate.

Hybrid laser for optical communications, and transmitter, system, and

A polarization insensitive optical device is disclosed which is capable of providing direct optical amplification of an input signal of unknown (and possibly varying) polarization. A polarization diversity technique is utilized wherein a polarization beam splitter is used to divide the incoming signal into orthogonal components of known polarization (TE,TM). The orthogonal components are then separately amplified, using a semiconductor laser as the amplifying device. The amplified components are then recombined, either optically or electrically, to form the final output signal.

Polarization insensitive optical communication device utilizing optical

Highly frequency-selective reflectivity is realized in an optical device including a waveguide and an evanescent-field coupled grating resonator cavity. The device may include a light source and serve as a low-chirp, narrow-linewidth communications laser for use, e.g., for transmission over a fiber having non-negligible dispersion and also in wavelength-multiplexed coherent systems.

Narrow-linewidth resonant optical device, transmitter, system, and method

A light transmitter comprising a cleaved-coupled cavity laser and stabilization means to maintain the laser in single longitudinal mode operation is described. '

Stabilized cleaved-coupled cavity laser

A laser-driven interferometric signal sensing system has a cleaved-coupled cavity laser with separate stabilization servo loops of different time constants for the modulator and laser sections thereof. The laser section is biased above lasing threshold, and its stabilization loop is operated at a frequency twice the frequency of laser section bias current modulation. A laser loop feedback error signal is a function of predetermined, environmental-type, parameter variations in the sensing location and is processed to be a function of the second derivative of interferometer output intensity with respect to laser section current. That error signal is applied to modify laser section bias current in a direction to zero out the feedback signal.

Cleaved-coupled-cavity-laser-driven system for measuring small signals

An analog-to-digital converter using a frequency tunable laser having output radiation of a frequency determined by the input voltage to the laser is described.

High speed analog-to-digital converter

Frequency shift keying optical communications devices using a cleaved coupled cavity laser are described. The cleaved coupled cavity laser comprises first and second laser diode sections which are mutually optically coupled to each other and means for adjusting the refractive index of the first and second sections relative to each other. The cleaved coupled cavity laser is part of a light source which further comprises means for selecting at least one desired output frequency from a group of at least two output frequencies.

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New Providence, NJ, United States of America

Nils A Olsson