Multichannel demultiplexer/demodulator technologies for future satellite communication systems

NASA-Lewis' Space Electronics Div. supports ongoing research in advanced satellite communication architectures, onboard processing, and technology development. Recent studies indicate that meshed VSAT (very small aperture terminal) satellite communication networks using FDMA (frequency division multiple access) uplinks and TDMA (time division multiplexed) downlinks are required to meet future communication needs. One of the critical advancements in such a satellite communication network is the multichannel demultiplexer/demodulator (MCDD). The progress is described which was made in MCDD development using either acousto-optical, optical, or digital technologies

Optical Channelizer Evaluation Using Empirical Data and Simulation

Westinghouse Electric Corporation Division under NASA contract NAS3-25865 developed a proof-of-concept (POC) multichannel demultiplexer implemented as an acousto-optic radiofrequency (RF) with a spectrum analyzer. A detailed analysis of the experimental results indicate that the expected degradation caused by the acousto-optical channelizer is approximately 2.0 dB degradation at 10(exp -5) bit-error rate (BER) and 3.0 dB degradation at 10(exp -8) BER. This degradation may be quite acceptable when considering the excellent volume, mass, and power characteristics of acousto-optical channelizing relative to other technologies. In addition, system performance can be greatly improved by using digital pulse shaping in the modem and increasing the channel spacing from 40 to 45 kHz for 64 kbps quadrature phase-shift keying (QPSK) modulation

Recent Advances in Wavelength-Division-Multiplexing Plastic Optical Fiber Technologies

This work has been supported by the Spanish Ministry of Economía y Competitividad under the grant TEC2012-37983-C03-02

Interrogation of fibre Bragg grating sensors using an arrayed waveguide grating

We experimentally investigate the use of an arrayed waveguide grating (AWG) to interrogate fibre Bragg grating (FBG) sensors. A broadband light source is used to illuminate the FBG sensors. Reflected spectral information is directed to the AWG containing integral photodetectors providing 40 electrical outputs. Three methods are described to interrogate FBG sensors. The first technique makes use of the wavelength-dependent transmission profile of an AWG channel passband, giving a usable range of 500 με and a dynamic strain resolution of 96 nε Hz-1/2 at 13 Hz. The second approach utilizes wide gratings larger than the channel spacing of the AWG; by monitoring the intensity present in several neighbouring AWG channels an improved range of 1890 με was achieved. The third method improves the dynamic range by utilizing a heterodyne approach based on interferometric wavelength shift detection, providing an improved dynamic strain resolution of 17 nε Hz -1/2 at 30 Hz. © 2005 IOP Publishing Ltd

Interrogation of fibre Bragg grating sensors using an arrayed waveguide grating

We experimentally investigate the use of an arrayed waveguide grating (AWG) to interrogate fibre Bragg grating (FBG) sensors. A broadband light source is used to illuminate the FBG sensors. Reflected spectral information is directed to the AWG containing integral photodetectors providing 40 electrical outputs. Three methods are described to interrogate FBG sensors. The first technique makes use of the wavelength-dependent transmission profile of an AWG channel passband, giving a usable range of 500 με and a dynamic strain resolution of 96 nε Hz-1/2 at 13 Hz. The second approach utilizes wide gratings larger than the channel spacing of the AWG; by monitoring the intensity present in several neighbouring AWG channels an improved range of 1890 με was achieved. The third method improves the dynamic range by utilizing a heterodyne approach based on interferometric wavelength shift detection, providing an improved dynamic strain resolution of 17 nε Hz -1/2 at 30 Hz. © 2005 IOP Publishing Ltd

Optically Multiplexed Systems: Wavelength Division Multiplexing

Optical multiplexing is the art of combining multiple optical signals into one to make full use of the immense bandwidth potential of an optical channel. It can perform additional roles like providing redundancy, supporting advanced topologies, reducing hardware and cost, etc. The idea is to divide the huge bandwidth of optical fiber into individual channels of lower bandwidth, so that multiple access with lower-speed electronics is achieved. This chapter focuses on one of the most common and important optical multiplexing techniques, wavelength division multiplexing (WDM). The chapter begins with a quick historical account of the origin of optical communication and its exponential growth following the invention of erbium-doped fiber amplifier (EDFA) leading to the widespread adoption of WDM. Alternate multiplexing schemes are also briefly discussed, including time-division multiplexing (TDM), space-division multiplexing (SDM), etc. A typical WDM link and its components are then discussed with special focus on WDM Mux/demultiplexer (DeMux). Further, certain challenges in this field are addressed along with some potential solutions. The chapter concludes by highlighting some features and limitations of optically multiplexed WDM systems

Agile optical beam scanner using wavelength and space manipulations

An agile optical scanning scheme is proposed that uses wavelength manipulations for deflecting a free-space optical beam by selection of the wavelength of the light incident on a wavelength dispersive optical element. Using fast tunable lasers or optical filters, this scanner features microsecond domain scan setting speeds, single/multiple beam(s) in space, and large several centimeters or more diameter apertures for sub-degree angular scans. The beam scanning scheme offers simple control (via wavelength tuning). The paper also introduces space multiplexing for optical beam scanning and discusses various system architectures utilizing both space and wavelength multiplexing to achieve high speed optical scanning with coarse and fine tuning capability. Experiments described demonstrate high-speed, high resolution, wavelength tuned optical scanning in one-dimension (1-D), two-dimensions (2-D), and three-dimensions (3-D)

Optical Processing of Microwave Signals for Small Satellite Payloads

For low altitude small satellite applications performing electronic surveillance or communication transponding missions highly capable payloads are needed. Generally these spacecraft have low dwell times over the areas of interest and must receive, or search for, signals over a wide frequency band. This paper presents an approach to the implementation of optical processing in complex electronic systems intended to receive and operate on multiple radio frequency (or microwave) signals. The goal is to exploit the rapidly expanding field of linear and nonlinear optics to synthesize transponders and receiving systems for satellites and other platforms. The inputs are assumed to be microwave. The outputs are assumed to be microwave or electronic (digital). In between, the signal operations are performed optically. The focus of the effort is in the architecture for the electronic functions, that allow optical component realization. These elements perform the signal processing operations of: pulse signal detection and pulse parameter estimation; modulation and demodulation of AM, PM, and PM carriers; phase locked loop signal tracking; carrier element mixing (frequency shifting); signal filtering; and signal matched filter detection. The spatial optical processing of ordinary time waveform signals offers significant potential benefits. It inherently provides wide bandwidth, high carrier frequency, and fast response processing capability. A signal Fourier transforms can be performed with a simple lens. The second spatial dimension for parallel processing enhances the capability for exhaustive search of a signal space for parameters of interest. The two-dimensional optical implementation of switching and routing matches the channelized nature of many current communication systems. Increased optical implementations of electronic systems can take advantage of the rapid technological growth in applications and devices in this parallel discipline of optics to effect greater capabilities for the 1990\u27s

Optical reconfigurable demultiplexer based on Bragg grating assisted ring resonators

A polarization independent reconfigurable optical demultiplexer with low crosstalk between adjacent channels and high number of potential allocated channels is designed on silicon on insulator technology. On to off state transitions can be implemented by changing the coupling factor or the ring length. Wavelength selective switch units are cascaded to form the demultiplexer. Crosstalks below -30dB with 50GHz channel spacing and losses below 1.5dB in the off state are obtained from simulations. Designs using carrier dispersion effect and power consumption estimations are included.This work has been sponsored by the Spanish Economy and Education Ministries through grants (Ref.TEC2012-37983-C03-02).Publicad