Nortel Networks Corporation

Northern Telecom Limited

Douglas S Burbidge

Keith D Anderson

Bernard Villeneuve

Milorad Cvijetic

Daniel Gariepy

An optical repeater is described which integrates an erbium doped optical fiber amplifier (EDFA) with a dispersion equalizer (DE) based on fiber gratings. The dispersion equalizer is based on parallel connection of a plurality of fiber gratings, or on parallel connection of a cascaded plurality of fiber grating branches, each branch carrying a plurality of gratings coupled in series. Each grating in each branch is chirped to provide selective reflection at one of the plurality of signal carrier wavelengths so that the total optical bandwidth of the dispersion equalizer is enhanced, i.e. the total bandwidth for a specific signal carrier wavelength is the combined optical bandwidths of the gratings which provide the reflection at the wavelength. The use of multiple gratings for each wavelength improves the optical bandwidth of the equalizer compared with single grating designs, enhancing the effective bandwidth. Further, the grating DE is disposed between two fiber amplifier lengths which share a single pump laser. Thus, this arrangement provides dispersion compensation and loss compensation in an optical repeater of lower cost, and smaller size, compared to a system of similar performance configured using discrete components.

Optical repeaters for single- and multi-wavelength operation with dispersion equalization

An apparatus for simultaneously stabilising the output power and wavelength of a semiconductor laser is disclosed. A wavelength discriminating scheme is used to provide a wavelength error signal and an output power detection scheme is used to provide an output power level signal. The wavelength error signal is used to adjust the behaviour of a temperature sensor such that an automatic temperature control (ATC) module configured to maintain a pre-determined output from the temperature sensor, adjusts the actual laser temperature to minimize said signal. The output power level signal is directly delivered to an automatic power control (APC) module, which adjusts the drive current fed into the laser to minimize said signal using known control circuitry means. Adjusting the properties of the temperature sensor makes it possible for the apparatus to manipulate laser temperature and current to achieve simultaneous power, wavelength and temperature control, using the constant-temperature and constant-power external control modules used by semiconductor lasers that do not stabilize wavelength.

Laser module allowing simultaneous wavelength and power control

A thermoelectric cooler (TEC) is used to maintain an electronic component, for example, a laser diode, at a set temperature. A thermistor senses the temperature of the laser and through a first control loop causes current to be passed through the TEC so as to adjust the laser temperature. As the temperature of the hot side of the TEC increases above the temperature of the cold side of the TEC, the TEC's cooling efficiency gradually decreases. This is compensated for by adding a second control loop which senses the TEC current and provides an additional gain proportional to the TEC current in the cooling sense. This additional gain is added to the gain provided by the first control loop. The result is a stable, highly responsive temperature controller at all points of the TEC operating range.

Thermoelectric cooler control circuit

An optical repeater is described which integrates an erbium doped optical fiber amplifier (EDFA) with a dispersion equalizer (DE) based on fiber gratings. The dispersion equalizer is based on parallel connection of two fiber gratings for single carrier wavelength operation, and on parallel connection of a cascade of two fibre grating branches, each carrying a plurality grating elements chirped for different wavelengths, for WDM operation at a plurality of wavelengths. The use of two gratings sections for each wavelength improves the optical bandwidth of the equalizer compared with single grating designs, doubling the effective bandwidth. Further, the grating DE is disposed between two fiber amplifier sections which share a single pump laser. Thus, this arrangement provides dispersion compensation and loss compensation in an optical repeater of lower cost, and smaller size, compared to a system of similar performance configured using discrete components.

Optical repeaters for single-and multi-wavelength operation with

A multiple path electro-optic transducer comprises a plurality of electro-optic elements arranged in an array in a device package with electrical connections thereto. A lens tube having a lens, such as a graded index (GRIN) lens, therein is supported so that an axis of the lens is perpendicular to and aligned with the array and so that the array is imaged by the lens in a plane of an outer end of the lens tube. An optical fiber connector comprises a ferrule having a bore therein and a plurality of optical fibers extending through the bore in an array corresponding to the array of electro-optic elements, the ferrule and fibers being positioned, by a cylindrical sleeve over the lens tube and ferrule, so that ends of the fibers lie in the plane of the outer end of the lens tube whereby light emitted by each of the electro-optic element is focused by the lens onto a respective one of the fibers. A mechanical coupling is provided by a bayonet connection between the optical fiber connector and the device package.

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Kanata, Canada

Douglas S Burbidge