Northern Telecom Limited

Bruce A Richardson

Douglas James Beckett

Christopher Edgar Falt

David M Adams

Claude Rolland

Jozef Finak

Robert A Bruce

A semiconductor-based optical phase-modulating device has first and second pairs of phase-fixing electrodes bracketing a pair of phase-modulating electrodes. The phase-fixing electrodes fix electric fields across end regions of the phase-modulating device to reduce distributed resistance and capacitance of the phase-modulating device, thereby improving the frequency response of the phase-modulating device. The optical phase-modulating device is particularly applicable to use in integrated optic Mach-Zehnder interferometers used for optical signal modulation.

Optical phase-modulating devices and methods for their operation

A method of reducing thermally-induced emission wavelength shift in laser diodes. In addition to the conventional ridge contact for supplying the modulation current to the laser diode a second ridge contact is formed on the device. A compensation current of substantially the same frequency as the modulation current but having an opposite phase is applied to the second contact. This compensation current is selected to substantially neutralize the transient temperature variations due to changes in the modulation signal and result in a generally steady state thermal situation.

Method of reducing the thermally-induced shift in the emission

In a method and apparatus for stabilizing the emission spectrum of a semiconductor laser diode, an external optical cavity is coupled to the laser diode to couple light from an active region of the laser diode to the external cavity and from the external cavity to the active region of the laser diode. The phase of light coupled from the external cavity to the active region of the laser diode is dithered about a phase operating point at a dither frequency. A component of the forward voltage across the laser at the dither frequency is sensed and a feedback signal indicative of the amplitude of said component of the forward voltage and the phase of said component of the forward voltage relative to the phase of the dither is generated. The phase operating point is changed in response to the feedback signal to minimize the amplitude of said component of the forward voltage. The method and apparatus are useful for stabilization of laser diodes used in high performance optical communications systems.

Method and apparatus for stabilizing the spectral characteristics of a

A direct coupled FET logic (DCFL) circuit element has an active FET with source connected to a low reference voltage and drain connected through a pull-up FET to a higher reference voltage. An input is applied to the gate of the active FET and the output is taken from its drain, the pull-up FET having its gate connected to its source. In depletion mode configuration, a photodiode is connected to the gate of the active FET, the photodiode energizable to downwardly shift the gate voltage. In enhancement mode configuration, a photodiode is connected between source and gate of the pull-up transistor and is energized to shift the gate voltage upwardly. The photodiodes are integrated with the active and pull-up FETs and are energized by light or decay radiation.

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Nepean, Canada

Bruce A Richardson