Optimetric Measurements with Continuous Optical Carriers Phase of Coherent Optical Communication

We propose to perform a study and experimental demonstration of ultra-high precision optimetric measurements (50 nm range error, 50 nm/s ranging rate error) with continuous optical carrier phase measurement on a coherent optical communication system. This approach improves optimetric measurement sensitivity by orders of magnitude vs. the current RF or RF over optical based optimetrics (10 µm range error, 10 µm/s ranging rate error). It will be game changing technology with such high precision ranging and high bandwidth communication. It will service both science and NAV/COMM at a new level of ranging precision and comm capacity. It will also advances the state-of-the-art for the optical comm system with high bandwidth and high precision ranging. It will be an enabler for precision formation flying missions that include: virtual sensors, sensor webs, large-number-multi-spacecraft distributed missions, autonomous rendezvous & docking; and enabler for gravitational based small-sat scientific missions.

Continuous optical phase measurement improves ranging accuracy by orders of magnitude due to the nature of much higher optical carrier frequency (4 to 5 orders of magnitude higher than RF). To demonstrate this phase measurement over optical communication links, our study will leverage the vast technology progress in the fields: 1. High speed coherent optical communication (Telecomm) (>100 Gbit/s) with photonic integrated circuit (PIC) and high speed analog and digital electronics.  2. Low noise laser source for gravity wave measurement (LISA) enables continuous optical phase measurement over long distance (>1 million km). This study will leverage the state of art hardware from both fields to demonstrate close LISA grade phase measurement accuracy and greater than 100GBPS data communication capability. Furthermore, we propose two more experiments to be implemented on the platform by taking advantages of wavelength division multiplexing (WDM). 1. WDM combines a second channel with low noise CW laser. It further improves the phase measurement accuracy by avoiding high data rate (>25 GHz) phase modulation introduced noise. 2. WDM combines two more CW optical channels, then performs a cross correlation among these two channel. This operation enhances the common mode signals (the relative distance of the two satellites) and suppresses uncorrelated noises (electronics, laser, and digital noised). It will lower the instrument noise floor, reduce the hardware complexity, and hence further reduce the SWaP. This proposal also leverages last year’s CIF/IRAD project “High Precision RF Ranging and Range Rate Measurements over Optical Carrier and Laser Communication in Cubesat Platform” on both technologies and methodologies. The success of this study will provide platform with both ranging over continuous optical phase (~50 nm error) and high rate coherent optical communication.