Dual Head Pulse Interval Modulation (DH-PIM) is a modulation technique using in optical wireless communications. In this paper, the performance of DH-PIM is analyzed in the presence of intersymbol interference. The channel impulse response and symbol error rate versus normalized delay spread are discussed. A soft-decision decoding technology is presented, which can improve the performance of DH-PIM.
In the optical wireless communications systems, modulation schemes such as PPM, DPPM are often used because of its power efficiency. This paper presents a modified DPPM modulation technique for optical wireless communication. We study the properties of IDPPM and compare the power and bandwidth efficiency of OOK, PPM, DPPM and IDPPM. Also we analyse the packet-error probability on ideal distortionless channels with AWGN and examine the detection technology of the system. Finally we show the improving of performance using IDPPM modulation.
Now, single-mode optical fiber has been widely applied in communication systems and the users of optical fiber have migrated to longer transmission wavelengths, which results in the task of optical fiber measurement becoming more difficult. A method measuring optical fiber properties such as fiber loss and attenuation is optical time domain reflectometer (OTDR) measurement. Conventional OTDRs have a limitation: the trade-off between signal-to-noise ratio and response resolution. This paper presents an approach that applies spectrum-spread techniques to remedy this limitation, and improves dynamic range and reduces measurement time without sacrificing response resolution.
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