Optical Hybrid Integrated Circuits
There is an increasing demand for advanced optic al communication systems to deal with the enormous data flow that will arise in the emerging multimedia era. These systems require low-cost and highly functional optical modules. However, convent ional opti
- PDF / 4,637,349 Bytes
- 38 Pages / 439 x 666 pts Page_size
- 74 Downloads / 223 Views
Optical Hybrid Integrated Circuits
Yasufumi Yamada, Yuji Akahori, and Hiroshi Terui
10.1
Introduction
There is an increasing demand for advanced optical communication systems to deal with the enormous data flow that will arise in the emerging multimedia era. These systems require low-cost and highly functional optical modules. However, conventional optical modules based on micro-optics consist of a large number of components including laser diodes (LD), lenses, mirrors, prisms and fibres. The use of these elements also results in the need for specially designed stems or sub carriers for constructing the modules. Moreover, these components are assembled by an active alignment procedure which requires monitoring via the activation of an LD and a photo diode (PD) or the excitation of guided light in the optical components. Although this procedure ensures a micron or submicron order alignment accuracy, it tends to become complicated and time-consuming. Therefore, there is a limit to the possibility of cost reduction with the conventional optical module. In addition, it is difficult to use micro-optics type modules as highly functional devices such as multi-channel wavelength or frequency selectors. To overcome this problem, it appears essential to develop a new optical module technique which meets the following requirements. First, the new technique should reduce the optical-module assembly cost and be suitable for mass production. Second, it should be applicable to a wide range of applications. In other words, it should be possible to use the same technique to fabricate not only simple optical transmitters and receivers but also highly functional modules for optical signal processing. Third, the module configuration should be compatible with electronic assembly technology. This is because the optical module is typically used with electronic circuits after they have been assembled on an electronic board. In the field of electronics, integrated-circuit technology has been successful in providing highly functional and low-cost large-scale integrated circuits (LSIs). By analogy with electronics, optical integrated circuits are expected to meet these requirements via the integration of passive and active optical elements on a substrate or on a chip. There are two approaches to optical integration: monolithic and hybrid. With monolithic optical integration all the optical elements are formed on a semiconductor chip (see Chap. 11). This is based on the same concept as electronic ICs or LSIs. However, there are some N. Grote et al. (eds.), Fibre Optic Communication Devices © Springer-Verlag Berlin Heidelberg 2001
10
Optical Hybrid Integrated Circuits
377
significant differences between electronic and optical integration, as shown in Table 10.1, and these differences seem to make monolithic integration rather difficult. With electronic integration, most functions are implemented on a silicon chip and their integration density is becoming higher and higher. By contrast, optical functions are currently implemented by us
Data Loading...
