We report on advances in polymeric waveguide technologies developed worldwide for the telecom and datacom markets, and we describe in detail one such technology developed at AlliedSignal. Optical polymers are versatile materials that can be readily formed into planar single-mode, multimode, and microoptical waveguide structures ranging in dimensions from under a micrometer to several hundred micrometers. These materials can be thermoplastics, thermosets, or photopolymers, and the starting formulations are typically either polymers or oligomers in solution or liquid monomers. Transmission losses in polymers can be minimized, typically by halogenation, with state-of-the-art loss values being about 0.01 dB/cm at 840 nm and about 0.1 dB/cm at 1550 nm. A number of polymers have been shown to exhibit excellent environmental stability and have demonstrated capability in a variety of demanding applications. Waveguides can be formed by direct photolithography, reactive ion etching, laser ablation, molding, or embossing. Well-developed adhesion schemes permit the use of polymers on a wide range of rigid and flexible substrates. Integrated optical devices fabricated to date include numerous passive and active elements that achieve a variety of coupling, routing, filtering, and switching functions.Index Terms-Datacom, dense wavelength-division multiplexing (DWDM), interconnects, low loss, polymers, telecom, thermooptic effect, tunable filters.
We review and contrast key technologies developed to address the optical components market for communication applications. We first review the component requirements from a network perspective. We then look at different material systems, compare their properties, and describe the functions achieved to date in each of them. The material systems reviewed include silica fiber, silica on silicon, silicon on insulator, silicon oxynitride, sol-gels, polymers, thin-film dielectrics, lithium niobate, indium phosphide, gallium arsenide, magneto-optic materials, and birefringent crystals. We then describe the most commonly used classes of optical device technology and present their pros and cons as well as the functions achieved to date in each of them. The technologies reviewed include passive, actuation, and active technologies. The passive technologies described include fused fibers, dispersion-compensating fiber, beam steering, Bragg gratings, diffraction gratings, holographic elements, thin-film filters, photonic crystals, microrings, and birefringent elements. The actuation technologies include thermo-optics, electro-optics, acousto-optics, magneto-optics, electroabsorption, liquid crystals, total internal reflection technologies, and mechanical actuation. The active technologies include heterostructures, quantum wells, rare-earth doping, dye doping, Raman amplification, and semiconductor amplification. We also investigate the use of different material systems and device technologies to achieve building-block functions, including lasers, amplifiers, detectors, modulators, polarization controllers, couplers, filters, switches, attenuators, isolators, circulators, wavelength converters, chromatic dispersion compensators, and polarization mode dispersion compensators. Some of the technologies presented are well established in the industry and in some cases have reached the commodity stage, others have recently become ready for commercial introduction, while some others are still under development in research laboratories and require significant progress in fabrication and assembly processes before they become commercially viable.
The demand in optical networking for photonic components that meet performance criteria as well as economic requirements has opened the door for novel technologies capable of high-yield low-cost manufacturing while delivering high performance and enabling unique functions. The most promising new technologies are based on integrated optics. Integration permits the parallel production of complex multi-function photonic circuits on a planar substrate. Polymeric materials are particularly attractive in integrated optics because of their ability to be processed rapidly, cost-effectively, and with high yields; because they enable power-efficient dynamic componentry through thermo-optic and electro-optic actuation; and because they allow to form compact optical circuits by offering large refractive index contrasts (index difference values between waveguide core and cladding). We compare the properties of optical polymers with those of other material systems utilized in integrated optics. We present an up-to-date snapshot of the global effort in optical polymer material development. We describe the criteria that optical polymers need to meet in order to be viable for commercial deployment. We review the state of the art in polymeric integrated optical components including switches, attenuators, filters, polarization controllers, modulators, lasers, amplifiers, and detectors. We further emphasize the practicality aspect by conveying which technologies have been productized successfully, which ones are ready for commercial introduction, and which ones are still under development in research laboratories.
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