lectrical Wavelength Demultiplexing esign, Fabrication, and Analysis

An optical-to-electrical wavelength demultiplexing detector has been fabricated using a short length of twin-core optical fiber and an integrated bi-cell detector. The twin-core fiber splits 1325 and 1535 nm input signals onto different out- put cores, thus directing each demultiplexed channel onto the spatially separated active areas of the bi-cell. We discuss the de- sign, fabrication, and post-tuning techniques used to successfully demonstrate the wavelength demultiplexing functionality of the device and present some preliminary results from an assembled laboratory prototype. I. INTRODUCTION 0 ENABLE the vast information carrying capacity of optical fibers to be exploited to its full potential, it is necessary to overcome the current information bottle-neck in the copper access network by deploying fiber directly to the business or home. Although many of the optical and opto-electronic devices needed for the local loop have simple functionality, it is imperative that they can be fabricated inex- pensively if they are to allow cost-effective deployment of a fiber-in-the-loop network. In this paper, we describe a compact device that combines optical wavelength demultiplexing with the simultaneous detection of both demultiplexed channels. The combination of both functions into a single, integrated package will allow savings in both cost and size, compared to concatenated conventional devices with the same functionality. A schematic of the optical-to-electrical wavelength de- multiplexing detector is illustrated in Fig. l. The two chan- nels to be demultiplexed enter the device via a single-core telecommunications fiber pigtail and are typically carried by wavelengths in the 1300 nm and 1550 nm windows. Both input signals are launched, via the pigtail fiber, into one core of a short length of twin-core fiber (TCF) which performs the demultiplexing action. This is achieved by splitting the two