Assessment of the effective performance of DPSK vs. OOK in satellite-based optical communications

Abstract

This paper reports on the assessment of the communication performance of DPSK-and OOK-based free-space optical (FSO) links in satellite-based applications, including LEO downlinks, LEO inter-satellite links, and feeder links for GEO Satellites. The performance is assessed by means of simulations as well as transmission experiments at 10 Gbps. The impact of optical filter bandwidth, optical delay-line-interferometer accuracy, frequency offset between transmitter laser and receiver, is quantified. OOK performance critically depends on transmitter extinction ratio, and proves robust to Doppler-induced frequency offsets. DPSK is sensitive to any laser wavelength drift and offset with the DLI response. Nevertheless, compensation of this drift is considered manageable, making it possible to maintain the 3dB advantage of DPSK vs. OOK in practical use conditions. INTRODUCTIONWith their potential for much higher capacity, smaller beam divergence, and lower terminal mass, volume and power, free-space optical (FSO) communication links are anticipated to dramatically exceed the performance of traditional radio-frequency-based solutions in an increasing number of satellite-based applications. In-orbit demonstrations so far were based either on simple On-Off Keying (OOK) with direct detection, or on Binary Phase-Shift Keying (BPSK) with complex homodyne detection 1 . Differential Phase-Shift Keying (DPSK) is compatible with optical demodulation and direct detection, thus offering the advantage of about 3dB higher noise tolerance at affordable added complexity 2 . Even though it has been considered for a long time 3 , only a few forthcoming FSO link demonstrations in space, namely LCRD 4 and JDRS 5 , will operate DPSK, and its effective suitability for other space applications is still under assessment. The present paper aims at evaluating the impact of critical parameters on DPSK transmission performance in satellitebased FSO communications, with a special attention paid to direct-to-the-Earth LEO down-links, inter-satellite links (ISL) in LEO constellations, and feeder links to high-throughput GEO satellites. The specific requirements deriving from the Doppler effect are taken into account. The theoretical performance of 10 Gbps DPSK-and OOK-based optical communication links, established by means of a commercial simulation software tool, are reported with Non-Return-to-Zero (NRZ) coding. Then, NRZ DPSK and OOK transmission experiments at 10 Gbps channel rate are reported and the results are compared. An experimental assessment of the critical link elements has been carried out and their influence on the Bit Error Rate (BER) performance has been quantified. Such parameters include optical filter bandwidth, optical delay-line-interferometer accuracy, frequency offset between transmitter laser and receiver. SATELLITE-BASED FSO COMMUNICATION APPLICATIONSFSO communications hold the potential to offer unrivalled advantages over RF counterparts, mostly stemming from the large difference in wavelength. Moving to higher carrier freque...

Link Budget Analysis for Free-Space Optical Satellite Networks

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“…We consider OOK as the optical link's modulation scheme. We use curve fitting technique to find the receiver sensitivity as -35.5 dBm for OOK modulation with 10 Gbps data rate and 10 −12 bit error rate from [7]. We consider P req as -35.5 dBm and set the LM as 3 dB.…”

Power and spectrum efficiencies of an optical satellite uplink with spatially diverse beams and incoherent combining

“…The paper is structured as follows. In §2, an analytical model is presented for the signal-to-noise ratio (SNR) of an optical direct-detection receiver with pre-amplification [8]. The SNR formula is extended to multiple diversity channels with a dependence on specific filter bandwidths.…”

“…The receiver model is marked in Figure 1 and consists of an optical amplifier, an optical filter, a photodetector and an electrical filter before data and clock are recovered. In the pre-amplified optical receiver, the amplified spontaneous emission (ASE) noise dominates all other noises [8]. Therefore, we must determine the powers of the ASE noise components to estimate the SNR.…”

High-performance DFB laser module for space applications: the FP7 HiPPO achievements from chip fabrication to system validation

“…The applicability of HiPPO technology for free-space optical communication links was demonstrated using the fiberbased test-bed shown in Figure 12. Details about the test-bed can be found in 7 . Bit-error-rate (BER) measurements were first performed with a commercial laser from G & H, and then with an HiPPO laser with +17 dBm output power.…”