Dispersion Compensator in Transmission using Tilted Chirped Fiber Bragg Grating Pair

摘要

Chromatic dispersion is an intrinsic property of optical fibers that allows an optical pulse to spread as it propagates along the fiber and spread more severely as the propagation distance and the data rate increase. With the increasing demand for high-bit-rate optical communication system, chromatic dispersion compensation in optical fibers has become a crucial issue. Thus, various methods to compensate for chromatic dispersion in high-speed optical systems have already been reported, including dispersion-compensated fibers (DCFs), a compensator using a pair of mode converters, dispersion-compensating technique based on a holey fiber and DCFs, and fiber gratings, such as fiber Bragg grating (FBG) and long-period fiber grating (LPFG) [1-4]. A dispersion compensator using a DCF has a nonlinear effect and needs to be spliced with an existing installed optical fiber network, thereby increasing the installation costs due to additional equipment. However, the use of chirped fiber gratings as a dispersion compensator has received considerable recent attention due to their low-insertion loss, fiber compatibility, simple fabrication, and passive operation. LPFGs fabricated with a relatively high delta value as an efficient dispersion compensator have also been proposed for dispersion compensation [5]. Based on choosing the length of the grating and refractive index modulation, a significant dispersion compensation can be achieved over a reasonable bandwidth using a high negative dispersion. However, this device requires coupling to a very high order cladding mode, which is highly prone to bend losses.