ACCURATE ANALYTIC EXPRESSIONS FOR GAIN IN A PR3- ZBLAN FIBER AMPLIFIER USING MODIFIED GAUSSIAN FIELD FUNCTIONS( )

Pr3+: ZBLAN fiber amplifiers are likely to be important components for 1.3 mum fiber systems. Efficient amplifiers require high DELTAn small -core fibers. Expressions for the gain of such amplifiers have been de rived. To obtain useful analytic expressions, it is necessary to appro ximate the mode field distribution with a simple function. For this ty pe of fiber, the usual Gaussian is not a good approximation, resulting in poor predictions of amplifier performance. This paper describes th e use of a modified Gaussian function which better approximates the mo de field distribution. It is shown by comparison to a full numerical s olution that the analytic expressions based on this modified Gaussian are significantly more accurate.