Detection modules for FSO receiver operating in the wavelength range of 8-12 um

Abstract

In this paper some constructions and test results of new detection modules for Free Space Optics (FSO) operated in the 8-12μm wavelength range are presented. In this spectrum, FSO communication is less sensitive to atmosphere features. The main requirements for detectors construction applied in FSO receiver correspond to both operational and functional parameters. These devices should be characterized by high detectivity and operation speed. It is necessary to achieve low value of error rate in the case of high attenuation of laser beam and small-aperture receiving optics. In this way, the design of the FSO transceiver is simplified. In practice, detection performance close to fundamental limits are required. Additionally, for the present optical links, subnanosecond response time is also very important. This can be achieved using of HgCdTe photodiode in the form of modified N+pP+ heterostructure with immersion lens, reverse biasing and TEC cooling. Immersion lens enables optimization of the detector physical dimensions, decreasing detector capacity and time constant detector. The high detectivity of the detection module was achieved by both matching the photodiode to the preamp and minimizing noises. The paper is review of designing and investigation process of the detection modules for FSO application. Some results of the performed simulations and experiments are also discussed. Finally, further refinements will be conducted taking into account parameters of FSO receiver.