At&t Bell Laboratories

Lucent Technologies Inc.

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

Bryon L Kasper

Fridolin L Bosch

Osamu Mizuhara

Joseph M Kahn

A laser transmitter that includes a heating element coupled to the laser package and controlled to allow the laser to be kept at a higher temperature than ambient when low temperature extremes occur, thus limiting the range of wavelengths output by the laser over a given temperature range. The laser transmitter includes a semiconductor laser having an associated operating temperature; a laser driver circuit coupled to the semiconductor laser to control a modulation current and bias current conducted by the semiconductor laser; a heating element thermally coupled to the semiconductor laser; and a heating control circuit that (i) senses a temperature substantially representative of the ambient temperature surrounding the laser transmitter, (ii) energizes the heating element to provide heat to the semiconductor laser only when the temperature substantially representative of the ambient temperature is sensed below a predetermined minimum temperature, and (iii) upon energizing the heating element, controls heating of the heating element based on the temperature substantially representative of the ambient temperature.

Wide temperature range uncooled lightwave transmitter having a heated

A transversal equalizer is realized by employing variable gain and delay in the amplification branches of a traveling wave amplifier. Specifically, by adjusting the gain and delay in each branch, the traveling wave type transversal equalizer may be adjusted to having a complementary frequency response in order to compensate for linear channel gain and phase ripples. This approach permits the transversal equalizer to be designed without the use of resistive splitter and combiner networks and, therefore, without the use of high gain amplifiers. Without such amplifiers, splitters and combiners, the smaller physical size, which is afforded thereby, allows the transversal equalizer to be easily assembled as a hybrid integrated circuit.

Traveling wave type transversal equalizer

A lightwave receiver, suitable for CATV applications, includes an input photodiode that is capacitively coupled to the differential inputs of a balanced amplifier. Biasing of the photodiode may be achieved by connecting the photodiode in series between a pair of resistors, with the differential inputs being taken from either side of the photodiode. This arrangement avoids the use of a transformer, which exhibits considerable high frequency loss, thereby avoiding the bandwidth limitation inherent with a transformer.

Lightwave receiver having differential input

An optical homodyne receiver is realized by employing two separate signal amplification paths in a balanced receiver configuration. Specifically, the relative phase difference between a received optical signal and a local oscillator signal is extracted from nodes which, from the point of view of an amplifier extracting a data component signal, are at ac ground. This approach permits a phase detector amplifier, which extracts the relative phase component, to be dc coupled in addition to having a higher transimpedance for lower thermal noise, and thus higher sensitivity. Additionally, by extracting the data and phase component signals at different points in a balanced receiver configuration, the data and phase amplifiers can be separately engineered for optimum performance.

Optical Homodyne Receiver

A receiver for optical signals using optical feedback between the output and input terminals of a transimpedance amplifier.

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Allentown, PA, United States of America

Bryon L Kasper