Invention Grant
- Patent Title: Integrated track-and-receive system for free-space optical communications
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Application No.: US17187726Application Date: 2021-02-26
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Publication No.: US11296787B2Publication Date: 2022-04-05
- Inventor: Kerri Cahoy , Paul Serra , Ondrej Cierny
- Applicant: Massachusetts Institute of Technology
- Applicant Address: US MA Cambridge
- Assignee: Massachusetts Institute of Technology
- Current Assignee: Massachusetts Institute of Technology
- Current Assignee Address: US MA Cambridge
- Agency: Smith Baluch LLP
- Main IPC: H04B10/112
- IPC: H04B10/112 ; G02B6/036 ; G02B6/028 ; H04B10/40 ; H04B10/50 ; H04B10/60 ; H04B10/25

Abstract:
A monostatic, beaconless fiber transceiver for free-space optical links infers fine tracking information using receiver optoelectronics and an injected pointing dither (nutation). A MEMS steering mirror fine-points the beams and injects the nutation. While this may disturb fiber coupling and transmit beam pointing, link loss becomes negligible for sufficient SNR. The SNR for links without point-ahead correction is about 35 dB to keep dither loss below 0.1 dB and RMS spatial tracking noise below a tenth of the beam divergence. Since the pointing and tracking bandwidth is much smaller than the receiver communication bandwidth, this SNR is achievable with appropriate filtering. For point-ahead correction, a single-mode fiber transceiver can reach up to about 1 beamwidth of correction, while a few-mode fiber transceiver can reach up to about 1.75 beamwidths due to improved coupling sensitivity at higher point-ahead offsets. Using a double-clad fiber with a secondary detector further reduces the incurred coupling loss.
Public/Granted literature
- US20210336697A1 Integrated Track-and-Receive System for Free-Space Optical Communications Public/Granted day:2021-10-28
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