Advances in Optical Components and Subsystems for Wavelength-Division Multiplexing Communications
Optical Engineering: The Journal of SPIE
The implementation of optical networks is considered to be the only solution to meet the future demands in the communications area. Despite the economic downturn, we received an encouraging level of submissions for this special section. Some of the papers included here were initially presented in the SPIE Information Technologies and Communications ͑ITCOM͒ conference on active and passive components and also in the optical computing algorithms and architecture conference. This special section
... comprised of 14 papers in the areas of wavelengthdivision multiplexing ͑WDM͒ components, systems and optimization, and applications. Between the source and the detector of an optical network, there are a number of important components technologies that make up the optical WDM network. The WDM components papers included in this special section are on interconnections, waveguides, fiber amplifiers, dispersion compensators, switching, add-drop multiplexers, clock recovery circuits, and detectors. In the first paper of this series, Kawai discusses interconnections between vertical-cavity surface emitting lasers ͑VCSEL͒ sources and fibers. Various alignment and packaging issues for developing interconnections between VCSEL sources and fiber waveguides are addressed in this paper. Waveguides consisting of heterostructured photonic crystals are the topic of the next paper by Ohtera et al. The authors describe an autocloning technology that minimizes the propagation loss to 0.1 dB/mm. To reduce the propagation loss while increasing the capacity and distance of an optical network, laser amplifiers are essential. In the next paper, Wang and Dutta present a model for an Er-Yb double-clad amplifier. Theoretical as well as numerical analysis of amplifier gains for various pump and signal powers are presented. One of the critical components for achieving high-bit-rate communications systems is polarization mode dispersion ͑PMD͒ compensation. In the next paper, Khosravani quantifies the effect of PMD on system performance. The author presents ways to compensate for the PMD and minimize signal distortion. Distortion may degrade the performance of optical switching devices. In the next paper, by Pérennou et al., cross talk performance of an acousto-optic switch caused by distortion induced by multiple modulation signals is analyzed. They show a degradation of signal-to-noise ratio caused by these intermodulation effects. The next three papers address components at the receiving end of the transmission system. Resonances characterized by maximum transmission/absorption have been used successfully for creating passive optical components. The paper by İşçi et al. uses a microsphere resonator to produce dips in the transmission characteristics, which can subsequently be used to construct an add/drop multiplexer. Add/drop multiplexers and demultiplxers at the receiving end need a stable clock source to operate. The next paper by Zhu et al. presents a method of clock recovery using a phase-locked loop in a Mach-Zehnder modulator. They show that it is possible to recover a 10-GHz clock from a 40-and 80-Gb/s data signal with only 50-fs jitter. Demultiplexer design using phased arrays is the topic of the last paper in the component category by Yehia and Khalil. Cascading small multimode interference phasar devices with high uniformity, they optimize a large structure with very low nonuniformity ͑less than 0.2 dB͒.