Abstract

We solve the coupled mode equations for uniform and chirped spatial mode couplers and find the bandwidth in terms of fiber and coupler parameters. We discuss operation in narrowband and broadband regimes and relate this to the device loss. In particular we demonstrate the possibility of combining low loss and wide bandwidth by introducing chirp in the coupler. Experimental results for a chirped and a uniform coupler having the same effective coupling length are compared and we obtain a broadening of the 99% coupling bandwidth by a factor of 5.4.

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