Accession Number : ADD018346
Title : Method and Apparatus for Improving the Sensitivity of Optical Modulators.
Descriptive Note : Patent, Filed 17 Mar 95, patented 1 Oct 96,
Corporate Author : DEPARTMENT OF THE NAVY WASHINGTON DC
Personal Author(s) : Esman, Ronald D
Report Date : 01 Oct 1996
Pagination or Media Count : 8
Abstract : An intracavity-modulated laser includes a gain element, an electro-optic modulator (EOM), a frequency selective coupler (FSOC), and an optical isolator coupled in such a way that a ring laser cavity is formed. The EOM selectively affects the optical input in intensity, phase, or frequency according the radio frequency (RF) input signal applied. The FSOC is a three port device that receives light at a first port and passes narrowbands of light out a second port and directs the remaining optical spectrum out a third port. The optical isolator assures single direction lasing. When the gain is sufficient to overcome the ring losses, the laser cavity will oscillate with longitudinal modes corresponding to the pass hands of the FSOC. The light exiting the second port of the FSOC is amplified by the laser gain element and is directed to the EOM. The EOM modulates each carrier (longitudinal mode) of the laser cavity thereby creating optical modulation sidebands associated with each carrier. The FSOC selectively couples the modulation sidebands out of the laser cavity. Since the FSOC contains no active elements, the frequency selective coupling operation is essentially noise-free. In this way an optical source is formed which can be modulated to frequencies limited only by the EOM bandwidths, reduces the RF input voltages required to produce a given modulation depth, effectively couples out only the modulation of the longitudinal modes allowing efficient use of optical components, and improves system performance without adding noise.
Descriptors : *LIGHT MODULATORS, *PATENTS, LASER CAVITIES, RING LASERS, ELECTROOPTICS, GAIN, SIDEBANDS, BANDWIDTH, OPTICAL CIRCUITS, WAVEGUIDE COUPLERS
Subject Categories : Electrooptical and Optoelectronic Devices
Distribution Statement : APPROVED FOR PUBLIC RELEASE