Laser communication transmitter and receiver design

Abstract

Free-space laser communication systems have the potential to provide flexible, high-speed connectivity suitable for long-haul intersatellite and deep-space links. For these applications, power-efficient transmitter and receiver designs are essential for cost-effective implementation. State-of-the-art designs can leverage many of the recent advances in optical communication technologies that have led to global wideband fiber-optic networks with multiple Tbit/s capacities. While spectral efficiency has long been a key design parameter in the telecommunications industry, the many THz of excess channel bandwidth in the optical regime can be used to improve receiver sensitivities where photon efficiency is a design driver. Furthermore, the combination of excess bandwidth and average-power-limited optical transmitters has led to a new paradigm in transmitter and receiver design that can extend optimized performance of a single receiver to accommodate multiple data rates. This paper discusses state-of-the-art optical transmitter and receiver designs that are particularly well suited for average-power-limited photon-starved links where channel bandwidth is readily available. For comparison, relatively simple direct-detection systems used in short terrestrial or fiber optic links are discussed, but emphasis is placed on mature high-performance photon-efficient systems and commercially available technologies suitable for operation in space. The fundamental characteristics of optical sources, modulators, amplifiers, detectors, and associated noise sources are reviewed along with some of the unique properties that distinguish laser communication systems and components from their RF counterparts. Also addressed is the interplay between modulation format, transmitter waveform, and receiver design, as well as practical tradeoffs and implementation considerations that arise from using various technologies.

Nanocrystallisation in oxyfluoride systems: mechanisms of crystallisation and photonic properties

“…Nowadays, it is required for medical applications and the transmission of information over long distances, including telephony, Internet traffic, long high speed local area networks, cable TV, etc. 214,215 The incorporation of RE ions into waveguides created a significant interest in finding materials which cover the broad available bandwidth of the spectra required for optical communications. Nowadays, Er 3z and Tm 3z doped fibres are useful in the third window of the spectra, since the emission occurs at 1?54 mm for Er 3z and between 1?450 and 1?480 mm for Tm 3z , while Pr 3z doped fibres operate in the second window, at 1?3 mm.…”

Interplanetary laser communications and precision ranging

“…In direct detection, the incoming received signal (weak) directly impinges on a photodetector (classical or photon-counting). In the coherent detection scheme, the incoming signal is overlapped with a local oscillator laser prior to detection www.lpr-journal.org with a photo-detector [25]. This approach effectively rejects background light, which can be a major source of noise during daytime communications.…”

“…To exceed today's state-of-the-art, link-limited downlink and uplink data-rate capabilities (e. g., 25 Mb/s downlink from shortest distance to Mars), the required spacecraft antenna size, RF transmit power, and system mass will have to increase appreciably, significantly stressing the capacity of conventional planetary spacecraft [10].…”

Performance of optically-preamplified PDM-BPSK-M-ary PPM and PDM-QPSK-M-ary PPM systems with finite extinction ratio

“…In Free-Space Optical (FSO) communications systems, it is desired to reduce the size, weight and power (SWaP) requirements of the optical terminals [1]. SWaP requirements can be reduced by improving the receiver sensitivity.…”

“…Non-return-to-zero (NRZ) and return-to-zero (RZ) on-off keying (OOK) modulation schemes have been extensively analyzed for FSO communications [1], [2]. The direct detection-based OOK, also known as intensity modulation with direct detection (IM-DD), has been widely implemented due to the simplicity of the optical receivers.…”