Passive and Active Glass Integrated Optics Devices
Optical integration technologies were uncovered early in the emergence of the optical telecommunication field. As early as 1973, a review reference such as [1 ] summarized some of the basic theoretical tools and device concepts later implemented in actual
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6.1
General Introduction
Optical integration technologies were uncovered early in the emergence of the optical telecommunication field. As early as 1973, a review reference such as [1] summarized some of the basic theoretical tools and device concepts later implemented in actual commercial components. Over the 25 years that ensued, the technology of planar devices on glass evolved, and they became available at the beginning of the 1990s, in the form of passive splitters. Glass planar devices are made with collective fabrication techniques close to those used in microelectronics. For this reason they are also part of integrated optics technology. One particular characteristic of integrated optics glass devices is that they have both optical inputs and optical outputs, in contrast to the transmitters and receivers described in Chaps. 3 and 4. As such, they offer a wide possible array of applications, which extends far over that of the commercially available passive splitters. Two main integrated optics technologies present the level of performance and reliability required for longdistance applications. The first one, mostly studied in the present chapter, is based on transforming a glass chemical composition by local ion exchange. The second type or group of technologies relies on doping an otherwise pure layer and then etching it to create the appropriate patterns and is considered in Chaps. 7 and 11. Before moving to the technical part, the reader should be aware of the rapid pace of change that optical techniques have undergone recently. The technology has now become market-pulled and its progress is governed by a combination of several factors: • The main market segment has evolved: The primary motor for growth in the optical telecommunication market has long been the long-distance segment. In the past, this market has mostly relied on semi-custom, single-function components assembled in simple optical subsystems. The more recent evolution, brought about by the combination of optical amplification and dense wavelength division multiplexing (DWDM), has moved requirements towards more complex subsystems. These, in turn, justify more integrated functions. N. Grote et al. (eds.), Fibre Optic Communication Devices © Springer-Verlag Berlin Heidelberg 2001
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Antoine Kevorkian
• Other market segments are growing: The ongoing European deregulation is predicted to be very effective in the actual competition it will generate. Since many European cities are closely located, the metropolitan area network will be at the heart of the expansion. The successful technological solutions will call for a better performance-to-cost ratio favorable to integrated technologies. Future evolution of the Access Network market will broaden the market even more, this time calling for very rugged, mass-produced devices. • The scope and technological performances of planar devices have improved: Ion-exchange planar or doped-silica devices present several areas of applications for passive as well as active functions. Table 6.1 shows how,
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