Northern Telecom Limited

Nortel Networks Corporation

Bookham Technology Limited

Hyung B Kim

Jin Hong

Vincent C So

Paul J Vella

Maurice Stephen O'Sullivan

Farideh Khaleghi

Toshihiko Makino

Mohsen Kavehrad

Toshi Makino

Jinghui Li

Jin J Hong

Bernard Villeneuve

The invention relates to compound cavity optical reflection modulation laser system providing frequency modulation of laser light by phase induced effective reflection modulation of the laser rear facet. The system includes a single mode gain coupled DFB laser integrated with a passive waveguide section to form a compound cavity modulation system. The waveguide includes a multiple quantum well region which is reverse biased to utilize the quantum Stark effect for voltage controlled refractive index modulation, thus providing phase modulation of the laser light. The phase modulated light is fed back to the laser to interfere with the light generated within the laser and to form the output light generated from the compound cavity. The interference effects cause modulation of the effective complex reflection of the rear laser facet which results in frequency modulation of the output light. If required, the frequency modulated light (FM) may be converted into intensity modulated (IM) light by using an additional narrow band optical filter, e.g. Mach-Zehnder interferometer.

Compound cavity reflection modulation laser system

A one dimensional series of complex coupled (gain or loss coupled) DFB semiconductor lasers is disclosed. Each laser comprises a multiple quantum well active region and a complex coupled grating having corrugations along a cavity length direction formed by periodically etching grooves through the active region. The grating has a period comprising a first section and a second section, wherein substantially all quantum wells are etched away from the second section providing no substantial photon generation in the second section. The depth of etching is defined so as to provide a substantial insensitivity of each laser to the external feedback and random facet variations and to ensure no substantial interaction between lasers in the series. The lasers in the series may further comprise means for tuning laser wavelengths around corresponding lasing modes and/or means for switching between the lasing modes. The series of lasers is also capable of simultaneous multi-wavelength generation, with the number of generated wavelengths being equal to a number of lasers in the series excited above threshold levels.

Series of strongly complex coupled DFB lasers

A complex coupled (gain coupled or loss coupled) distributed feedback (DFB) semiconductor laser, having two sections axially distinct along a cavity length direction, and two excitation means for independent pumping of corresponding sections of the laser in a master and slave type of pumping control, is provided. An extended continuous wavelength tuning range of the laser is obtained by selectively activating a left Bragg mode or a right Bragg mode across the stop band of the laser as a dominant lasing mode by the master and slave type of current injection control into different sections of the laser to alternate gain coupling and loss coupling mechanisms of laser operation, and further tuning a wavelength around the activated Bragg mode. Methods of operating the laser, enhancing a tuning range, and fabricating thereof are provided.

Two-section complex coupled distributed feedback semiconductor laser

A compact wavelength monitoring and control assembly for a laser emission source is provided comprising a narrow bandpass, wavelength selective transmission filter element, of Fabry-Perot etalon structure, through which a non-collimated beam from the laser source is directed onto two closely spaced photodetectors. For wavelength stabilization, the differential output of the two photodetectors is used in a feedback loop to stabilize the wavelength of the laser source to a desired target wavelength. Through the angular dependence of the wavelength transmission of the Fabry-Perot etalon, a wavelength variation from the source is converted to a transmission loss, which is different for the two photodetectors, so that the wavelength change is detected as a differential power change. The device functions as an optical wavelength discriminator in which the detector converts optical energy to current for a feedback loop for controlling the light source. A lens may be used to control the divergence of the light incident on the filter element to optimize power transfer. Optionally, wavelength tunability is provided by changing the angle of inclination of the Fabry-Perot etalon relative to the laser source. The system is compact and may be co-packaged within the same package as a laser emission source, overcoming coupling, space and power dissipation problems common with known external semiconductor laser wavelength control units.

Wavelength monitoring and control assembly for WDM optical transmission

Bidirectional WDM transmission at 2.5 Gb/s using a bidirectional erbium-doped fiber amplifier (EDFA) is demonstrated over a distance of 300 km. A symmetrical EDFA configuration with a frequency tunable reflection attenuator is used as a bidirectional amplifier. Experimental results show that the allowable gain of the EDFA can be increased significantly while the associated bit error rate BER penalty remains negligible.

Bidirectional optical amplifier

A bandwidth limiter for an optical fiber transmission path comprises a four-port optical coupler via which an optical signal is passed. A spliced optical fiber provides a loop, from an output to an input of the coupler, with a predetermined propagation delay and attenuation. An alternative arrangement uses two couplers which are coupled together via fibers of different length and hence propagation delay.

Growing community of inventors

Kanata, Canada

Hyung B Kim