Intraband and interband optical crosstalk in multiwavelength optical cross connects using tunable fiber Bragg gratings and optical circulators

Fiber Bragg grating (FBG) based wavelength division multiplexer (WDM) optical cross connect (OXC) is of great importance, which has the advantages of good performance and potential low cost. Optical crosstalk plays a major role in limiting practical implementations of an OXC. Crosstalk analyses presented so far generally focus on the traditional multiplexer/demultiplexer and optical switch based OXC architecture. In this paper, optical crosstalk in multiwavelength reconfigureable nonblocking OXCs using tunable FBGs and optical circulators (OCs) is discussed. Two crosstalk mechanisms, intraband and interband, are identified and analytical models are presented. Both first-order and second-order crosstalk contributions have been studied. For the intraband crosstalk, results show that the worst case coherent crosstalk is the dominant crosstalk, which is ~ 23 - 25 dB higher than the incoherent crosstalk, depending on the switching states of the 2 x 2 OXCs. For the interband crosstalk, results show that it is nonaccumulative and becomes very small with the increase of the number of fibers or the cascaded stages of 2 x 2 OXCs. However it deteriorates with the increase of the number of wavelengths per fiber.