Optical modulator

About: Optical modulator is a research topic. Over the lifetime, 14068 publications have been published within this topic receiving 196932 citations.

Generation of vector partially coherent optical sources using phase-only spatial light modulators

Abstract: Partially coherent beams (PCBs) of light can be highly directional, as from lasers, yet resistant to speckle and scintillation, as from LEDs. Generating PCBs with separate optical components for beam shaping and spatial coherence is complicated, and fundamentally limited. The authors control both shape and coherence using liquid-crystal spatial light modulators, and can produce two different classes of PCBs using the same simple optical setup. This work is immediately applicable in such diverse fields as medicine, directed energy, free-space optical communication, and manufacturing.

Return-to-zero modulator using a single NRZ drive signal and an optical delay interferometer

Abstract: We experimentally demonstrate and discuss a new technique for variable duty cycle return-to-zero (RZ) modulation, employing a phase modulator driven by a single electrical nonreturn-to-zero signal, and an optical delay interferometer. Unlike other methods for generating RZ, no synchronization between two electrical driving signals is needed.

Optical wavelength converters

Abstract: Devices and techniques for shifting the frequency/wavelength of an optical carrier wave are reviewed, with particular reference to applications in wavelength/frequency division multiplexed optical communication systems. Considered first are devices which make use of semiconductor laser amplifiers or oscillators. Some of these techniques come close to satisfying the requirements for a suitable wavelength shifter, though none appear to offer the potential for a transparent network independent of data modulation format. A second main category, using nonlinear optical materials, promises to satisfy the requirements for frequency translation in a network which is fully transparent to the modulation format. However, the conversion efficiencies currently available appear too low for cost-effective communication systems engineering so that further advances in nonlinear optical materials/techniques are still required. It seems likely that guided wave techniques will provide the best means of improving the efficiency by increasing the interaction length and the optical intensity for a given power. Schematic examples of such a converter are discussed. All of the existing techniques have some deficiencies compared to an ideal system so that wavelength conversion for optical communication systems is still a problem in search of a good solution.

Fiber optic continuous liquid level sensor

Abstract: A fibre optic sensor, particularly for ascertaining fluid levels, utilizes two cylindrical lightguides with regular perturbations to emit and/or accept light in a radial direction. Each waveguide is coupled to one (or more) light source and/or to one (or more) light detector. A light source such as a light emitting diode or laser diode is coupled to the lightguide which emits radially, illuminating a planar dielectric surface, which in the presence of a fluid with a low index of refraction, e.g. air, behaves as a mirror, coupling light via total internal reflection to the lightguide which accepts this light radially and channels the light to a light detector. In the presence of a fluid with a high index of refraction, for example water, at the planar dielectric surface the fluid dielectric interface becomes primarily transmissive, with relatively little light being coupled to the lightguide which accepts light radially. The optical signal received at the light detector is thus related to the depth of the planar dielectric surface which is immersed in liquid. Several different embodiments to achieve liquid level sensing, as well as a scheme for eliminating sensitivity to optical signal changes induced in the lead fibre, are disclosed.

Advanced LiNbO/sub 3/ optical modulators for broadband optical communications

Abstract: This paper describes advanced lithium niobate (LiNbO3) optical modulators for broadband optical communications. It includes 40-Gb/s ultralow voltage modulators, compact modulators and modulators for frequency comb generator and short pulse generation