A sequentially self-seeded Fabry-Perot laser for two-dimensional encoding/decoding of optical pulses

Multiwavelength optical pulse trains with variable two-dimensional (2-D) code patterns formed by a single encoder have been generated from a self-seeded gain-switched Fabry-Perot (F-P) laser for the first time. Mechanically tunable cascaded fiber Bragg gratings (FBG) are used to construct the reconfigurable encoder, which acts as a discrete nonlinear dispersive component in the subharmonically pulse-gated external cavity of the laser to generate multiwavelength pulse trains with a variable 2-D code pattern defined by the settings of the FBG string. Four distinct repetitive patterns (corresponding to four different 2-D codes) of optical pulse trains, each made up of up to four pulses generated sequentially with different wavelengths, have been produced at a repetition rate of 250 MHz. The output pulses obtained by this method are much more intense and stable than those obtained from a free-running F-P laser. Furthermore, the different pulse patterns obtained show that the scheme can allow easy switching among different 2-D codes by simply reconfiguring the FBG string. Hence this laser with the embedded reconfigurable encoder should be a viable optical source for incoherent 2-D fiber-optic code-division multiple access (FO-CDMA) applications. Near-error-free transmission of data at 250 Mbit/s employing this laser/encoder over 9.5 km standard single mode fiber has been successfully demonstrated, thus confirming its performance and viability for FO-CDMA.