Extended cavity fabry-perot laser assembly capable of high speed optical modulation with narrow mode spacing and wdm optical system including same

Abstract

An extended cavity Fabry-Perot laser assembly provides relatively narrow mode spacing while allowing relatively high speed optical modulation. The extended cavity Fabry-Perot laser assembly generally includes an exit reflector physically separated from a laser emitter (e.g., a gain chip) to extend the lasing cavity and narrow the mode spacing while maintaining a relatively small gain region in the laser emitter capable of higher speed optical modulation. The extended cavity Fabry-Perot laser assembly may be used in a multi-channel transmitter in a wavelength division multiplexed (WDM) optical system that selects a channel wavelength for the transmitter from among multiple channel wavelengths emitted by the laser assembly. The narrow mode spacing may be less than a WDM channel width, and more specifically, may be less than a channel passband of an arrayed waveguide grating (AWG) or other filter used to select the channel wavelength.

What is claimed is: 
     
         1 . An extended cavity Fabry-Perot laser assembly comprising:
 a laser emitter including a gain region for emitting light across a range of wavelengths including a plurality of channel wavelengths and a back reflector located at one end thereof, wherein the gain region has a gain region cavity length capable of optical modulation at a data rate of at least about 1 Gbps; and   an optical waveguide optically coupled to and physically separated from the gain region, wherein the light emitted from the gain region is optically coupled into a light coupling end of the optical waveguide and the optical waveguide includes an exit reflector, wherein an extended lasing cavity is formed between the back reflector and the exit reflector and configured to emit the laser light including the plurality of channel wavelengths, wherein the extended lasing cavity has a length such that a mode spacing of the laser light emitted from the lasing cavity is less than about 0.4 nm, wherein the gain region cavity has a length of less than about 1000 μm and the extended lasing cavity between the back reflector and the exit reflector has a length of at least about 9 mm.   
     
     
         2 . The extended cavity Fabry-Perot laser assembly of  claim 1  wherein the optical waveguide is an optical fiber. 
     
     
         3 . The extended cavity Fabry-Perot laser assembly of  claim 2  wherein the exit reflector includes a reflective coating on the light coupling end of the optical fiber. 
     
     
         4 . The extended cavity Fabry-Perot laser assembly of  claim 2  wherein the exit reflector includes a fiber Bragg grating at the light coupling end of the optical fiber. 
     
     
         5 . The extended cavity Fabry-Perot laser assembly of  claim 1  wherein the exit reflector includes a distributed Bragg reflector (DBR) in the optical waveguide. 
     
     
         6 . The extended cavity Fabry-Perot laser assembly of  claim 1  further comprising a lens for optically coupling the light emitted by the gain region into the light coupling end of the optical waveguide. 
     
     
         7 . The extended cavity Fabry-Perot laser assembly of  claim 1  wherein the extended lasing cavity between the back reflector and the exit reflector has a length such that the mode spacing of the laser light emitted from the extended lasing cavity is about 0.1 nm or less. 
     
     
         8 . The extended cavity Fabry-Perot laser assembly of  claim 1  wherein the exit reflector is located after the light coupling end of the optical waveguide such that the extended lasing cavity extends beyond the light coupling end of the optical waveguide. 
     
     
         9 . The extended cavity Fabry-Perot laser assembly of  claim 8  wherein the optical waveguide includes an optical fiber, and wherein the exit reflector is a fiber Bragg grating located within the optical fiber. 
     
     
         10 . The extended cavity Fabry-Perot laser assembly of  claim 8  wherein the optical waveguide includes at least first and second optical fiber segments, wherein the exit reflector is located between the optical fiber segments. 
     
     
         11 . The extended cavity Fabry-Perot laser assembly of  claim 1  wherein the plurality of channel wavelengths include wavelengths in the L-band. 
     
     
         12 . The extended cavity Fabry-Perot laser assembly of  claim 1  wherein the plurality of channel wavelengths include wavelengths in the C-band.