Simple Derivation of Approximate Crosstalk Expressions for Multicore Fibers With Core-Dependent Loss

Recently, rigorous and approximate expressions for evaluating direct crosstalk (XT), indirect XT, and backscattered XT in uncoupled multicore fibers (MCFs) with core-dependent loss (CDL) have been reported. The approximate expressions are very easy to use; however, it might be difficult to intuitively understand XT mechanisms, because the approximate expressions are derived from the rigorous expressions under some approximations. In this letter, for each of the direct XT, indirect XT, and backscattered XT in uncoupled MCFs with CDL, we derive another approximate expression on the basis of simplified coupled-power equations which can be easily solved. Compared with the previously reported approximate expressions, the newly derived approximate expressions have better approximation accuracy for large values of CDL and are sufficiently accurate for practical use.