Abstract

Concatenation of nonlinear all-optical switches offers considerable potential for the synthesis of digital switching characteristics with all the advantages that digital technology affords. Nonlinear interferometric switches such as the nonlinear optical loop mirror (NOLM) generally exhibit sinusoidal cw transmittance dependence on the optical power. The effect of concatenation is to transform this sinusoidal characteristic to one that is much more square. An important consideration in device concatenation is to minimize the component count necessary to optimize the characteristics. We have fabricated an all-optical switch with a digital characteristic that uses a single NOLM¹ in a double-pass configuration. In addition to economizing on components, use of a single NOLM ensures that the properties of the switch remain unchanged for the second pass. Our experiment is conducted with 100-ps pulses at a repetition rate of 76 MHz. The device is fabricated in a conventional single-mode fiber 2 km long. Switching powers of a few watts are used. A sharp on/off threshold is generated which is in good agreement with theory. Good isolation is obtained between the pulse trains circulating in the device, i.e., the device has the two ports necessary to demonstrate switching.

© 1991 Optical Society of America