All-optical signal processing techniques with fiber based devices

Abstract

The development of new optical devices and techniques has boosted new possibilities in many different topics. In these, the field of communications has been one of the most prolific, with the exponential growth of optical communications, fuelled by the explosion of the internet and the increased demand for “broadband for all”. However, today's optical networks are fairly static and operate within well-defined specifications. The addition of new nodes or the upgrade of existing links demands an enormous expenditure. A cost-effective implementation of future optical networks should accommodate old static networks, as well as new highly-efficient networks. It also should be intelligent, self-managed, monitored and dynamically-reconfigurable and should be able to accept new nodes in a plug-and-play manner. All-optical processing devices and techniques are a cost-effective solution for the implementation of these new paradigms in future optical networks. Such devices allow surpassing some of the limitations inherent to electric devices by keeping the signal in the optical domain, avoiding electrical-optical-electrical (OEO) conversions. In order to enable the reconfigurability of the network, all-optical devices should be transparent to modulation format, bit rate, protocol, as well as other requirements. Fiber based devices offer a cost-effective solution when compared to integrated technologies, maintaining the advantages of all-optical processing. For example, fiber Bragg gratings (FBG) are passive optical devices that can be designed with custom transfer functions for different applications such as optical filtering, dispersion compensation [1], pulse shaping etc. For example, the transfer function of a sinc-shaped FBG with a shading function in the spatial domain is a super-Gaussian with almost flat group delay response. This filter is a good candidate for format conversion between double sideband modulation (DSB) and vestigial sideband modulation (VSB). For this purpose, a grating was produced using a CW Ar ion laser emitting at 244 nm and an interferometric setup for the production of the UV fringes in a hydrogenated SMF fiber. all-optical processing, fiber Bragg gratings, optics communications.