We discuss conceptual designs for structured optical receivers that canalleviate the requirement for high peak-to-average power ratio inphoton-starved optical communication. The basic idea is to transmit sequencesof suitably modulated coherent light pulses whose energy can be concentrated ina single temporal bin on the receiver side through optical interference. Twoexamples of scalable architectures for structured receivers are presented. Thefirst one, based on active polarization switching, maps Hadamard codewordscomposed from the binary phase shift keying (BPSK) constellation onto thestandard pulse position modulation (PPM) format. The second receiver, usingsolely passive optical elements, converts phase-polarization patterns ofcoherent light pulses into a single pulse preserving a synchronized time ofarrival. Such a conversion enables implementation of a communication protocolequivalent to the PPM scheme but with distributed optical power provided thatthe intersymbol guard-time exceeds the pattern length.
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