Abstract

Optical signal processing using monolithically integrated semiconductor laser amplifier (SLA) structures will play an important role in future optical networks. In this paper we focus on the development of such devices for optical time-division multiplexing (OTDM) systems. Interferometer arrangements consisting of one or two SLAs are very attractive for this purpose. Here the cross-phase modulation due to the gain-saturation nonlinearity of SLAs provides the differential phase shift required for interferometric switching. Such devices are closely related to their all-fiber counterparts, namely, nonlinear optical loop mirror (NOLM) devices where Kerr effect in fibers is employed [1-3]. Figure 1 shows various possible nonlinear interferometer (NLI) structures for all-optical signal processing. Until recently, such devices were primarily assembled as nonlinear Sagnac interferometers (NSI) by using discrete SLA components incorporated within an optical fiber loop [4-8]. In such hybrid SLA/fiber devices it is usually necessary to employ the Sagnac configuration in combination with a polarization controller in order to handle the instability of the polarization state due to thermal/acoustic fluctuations. However, other hybrid interferometer arrangements like Mach-Zehnder interferometers (MZI) which exploit nonlinearities in passive waveguides and SLAs have also been reported [9-10], It follows that the development of these nonlinear interferometers as monolithically integrated devices is indispensable for their use in real system applications. Recently, we have realized the monolithically integrated interferometers and demonstrated their applications in all-optical demultiplexing and add-drop multiplexing up to 40 Gbit/s and 20 Gbit/s, respectively [11-13].

© 1996 Optical Society of America