10 Gb/s optical heterodyne receiver for intersatellite communications links

We present an optical heterodyne receiver for data rates up to 10 Gb/s. Its outer dimensions are 44x44x18 cm3, it weighs 16.5 kg and consumes 70 W of power. This optical receiver is single-mode fiber coupled to distribute the received signal from the outside of the spacecraft to the inside. This approach improves the ruggedness of the receiver system against shocks and vibrations. Under an ESA funded project, the photodiodes of this receiver have passed space qualification tests, such as Particle Impact Noise Detection tests, shock and vibration survivability, as well as proton and gamma radiation exposure. High receiver sensitivities (BER=1·10-9) of 390 photons/bit and 619 photons/bit were measured at 1550 nm for differential phase-shift keying (DPSK) and on/off keying (OOK), respectively. No low noise optical preamplifier (EDFA) was used in this case. These are one of the highest sensitivities reported for heterodyne detection of 10 Gb/s signals without using optical amplification. Avoiding the use of an EDFA allows to adapt the coherent receiver to other wavelengths such as 1064 nm. We also investigated the receiver sensitivity of the coherent receiver when combined with a low noise optical preamplifier. For 10 Gb/s DPSK and OOK sensitivities of 74 photons/bit and 132 photons/bit were measured, respectively.