Optical Signal Processing in Highly Nonlinear Fibers

2	Nonlinear Effects in Optical Fibers

2.1      INTRODUCTION

Conventional glass fibers for optical communications are made of fused silica and show an attenuation as low as 0.148 dB/km [1] with a broad low-loss optical window that covers about 60 THz, ranging from 1260 to 1675 µm [2]. A number of third-order nonlinear processes can occur in optical fibers [3]; these can grow to appreciable magnitudes over the long lengths available in fibers, even though the nonlinear index of the silica glass is very small (n₂=2.7 × 10⁻²⁰m²/W) [4].

Fiber nonlinearities fall into two general categories [3]. The first category of nonlinearities arises from modulation of the refractive index of silica by intensity changes in the signal (Kerr effect). This ...