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Results for “High data rate optical communications”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Multi-access laser communications terminal

The Optical Multi-Access (OMA) Terminal is capable of establishing up to six simultaneous high-data-rate communication links between low-Earth-orbit satellites and a host satellite at synchronous orbit with only one 16-inch-diameter antenna on the synchronous satellite. The advantage over equivalent RF systems in space weight, power, and swept volume is great when applied to NASA satellite communications networks. A photograph of the 3-channel prototype constructed under the present contract to demonstrate the feasibility of the concept is presented. The telescope has a 10-inch clear aperture and a 22 deg full field of view. It consists of 4 refractive elements to achieve a telecentric focus, i.e., the focused beam is normal to the focal plane at all field angles. This feature permits image pick-up optics in the focal plane to track satellite images without tilting their optic axes to accommodate field angle. The geometry of the imager-pick-up concept and the coordinate system of the swinging arm and disk mechanism for image pick-up are shown. Optics in the arm relay the telescope focus to a communications and tracking receiver and introduce the transmitted beacon beam on a path collinear with the receive path. The electronic circuits for the communications and tracking receivers are contained on the arm and disk assemblies and relay signals to an associated PC-based operator's console for control of the arm and disk motor drive through a flexible cable which permits +/- 240 deg travel for each arm and disk assembly. Power supplies and laser transmitters are mounted in the cradle for the telescope. A single-mode fiber in the cable is used to carry the laser transmitter signal to the arm optics. The promise of the optical multi-access terminal towards which the prototype effort worked is shown. The emphasis in the prototype development was the demonstration of the unique aspect of the concept, and where possible, cost avoidance compromises were implemented in areas already proven on other programs. The design details are described in section 2, the prototype test results in section 3, additional development required in section 4, and conclusions in section 5.

Source record↗
NASA NTRSDate not supplied

Laser Communications Relay Demonstration Optimetrics Experiment

Within this paper, we report on an Optimetrics experiment conducted on the National Aeronautics and Space Administration (NASA) Laser Communication Relay Demonstration (LCRD). The high precision two-way ranging is conducted on the optical communications link between the LCRD space terminal in a geosynchronous orbit and the Optical Ground Station 1 (OGS1) at Table Mountain, California, and is referred to as optimetrics ranging. The receiver to transmitter clock loopback is implemented in the LCRD space modem. A digital dual mixer time difference phase meter (DDMTD) is implemented in the OGS1 ground modem. The round-trip time is measured with the DDMTD by counting the frame and data clock ticks between transmitter and receiver frame synchronization markers for coarse range, and the relative phase of the transmit and receive clock for high precision range. This approach provides coverage for all potential ranges with no ranging ambiguity. The flight modem FPGA code was modified for frame and data clock loopback and the OGS1 FPGA code was modified for the DDMTD phase meter implementation. The experiment team conducted a 36-hour continuous ranging measurement. Preliminary two-way optimetrics ranging data show a noise floor of 3cm (rms). Based on our theoretical noise analysis and ground tests with spare flight modems, we expected one order of magnitude improvement on ranging precision. We are conducting detailed post data processing to identify the differences to further reduce the noise level and formulating an improved implementation approach for future missions. For reference and comparison, traditional Radio Frequency (RF) ranging between LCRD and OGS1 was conducted at the same time and indicates a ranging noise floor of 30cm(rms). Other telemetry and relevant environmental parameters such as weather and atmosphere temperature were also collected for offline data processing. The high precision ranging and range rate measurements from the laser communications data link clock and clock phase are performed simultaneously with continuous optical communication. No extra hardware added to existing system. This high precision optimetrics measurement implementation provides alternative ranging and range rate measurements for orbit determination (OD) and flight dynamics calculations with higher precision. We see significant improvement on OD for navigation upon implementation in future optical communication systems.

Rafael Garcia↗
NASA NTRS1982

Power efficient optical communications for space applications

Optical communications technology promises substantial size, weight and power consumption savings for space to space high data rate communications over presently used microwave technology. These benefits are further increased by making the most efficient use of the available optical signal energy. This presentation will describe the progress to date on a project to design, build and demonstrate in the laboratory an optical communication system capable of conveying 2.5 bits of information per effective received photon. Such high power efficiencies will reduce the need for photon collection at the receiver and will greatly reduce the requirements for optical pointing accuracy, both at the transmitter as well as the receiver. A longer range program to demonstrate even higher photon efficiencies will also be described.

Lesh, J. R.↗
NASA NTRS2012

Optical Phase Recovery and Locking in a PPM Laser Communication Link

Free-space optical communication holds great promise for future space missions requiring high data rates. For data communication in deep space, the current architecture employs pulse position modulation (PPM). In this scheme, the light is transmitted and detected as pulses within an array of time slots. While the PPM method is efficient for data transmission, the phase of the laser light is not utilized. The phase coherence of a PPM optical signal has been investigated with the goal of developing a new laser communication and ranging scheme that utilizes optical coherence within the established PPM architecture and photon-counting detection (PCD). Experimental measurements of a PPM modulated optical signal were conducted, and modeling code was developed to generate random PPM signals and simulate spectra via FFT (Fast Fourier Transform) analysis. The experimental results show very good agreement with the simulations and confirm that coherence is preserved despite modulation with high extinction ratios and very low duty cycles. A real-time technique has been developed to recover the phase information through the mixing of a PPM signal with a frequency-shifted local oscillator (LO). This mixed signal is amplified, filtered, and integrated to generate a voltage proportional to the phase of the modulated signal. By choosing an appropriate time constant for integration, one can maintain a phase lock despite long dark times between consecutive pulses with low duty cycle. A proof-of-principle demonstration was first achieved with an RF-based PPM signal and test setup. With the same principle method, an optical carrier within a PPM modulated laser beam could also be tracked and recovered. A reference laser was phase-locked to an independent pulsed laser signal with low-duty-cycle pseudo-random PPM codes. In this way, the drifting carrier frequency in the primary laser source is tracked via its phase change in the mixed beat note, while the corresponding voltage feedback maintains the phase lock between the two laser sources. The novelty and key significance of this work is that the carrier phase information can be harnessed within an optical communication link based on PPM-PCD architecture. This technology development could lead to quantum-limited efficient performance within the communication link itself, as well as enable high-resolution optical tracking capabilities for planetary science and spacecraft navigation.

Aveline, David C.↗
NASA NTRS2016

Low-Noise Free-Running High-Rate Photon-Counting for Space Communication and Ranging

We present performance data for low-noise free-running high-rate photon counting method for space optical communication and ranging. NASA GSFC is testing the performance of two types of novel photon-counting detectors 1) a 2x8 mercury cadmium telluride (HgCdTe) avalanche array made by DRS Inc., and a 2) a commercial 2880-element silicon avalanche photodiode (APD) array. We successfully measured real-time communication performance using both the 2 detected-photon threshold and logic AND-gate coincidence methods. Use of these methods allows mitigation of dark count, after-pulsing and background noise effects without using other method of Time Gating The HgCdTe APD array routinely demonstrated very high photon detection efficiencies ((is) greater than 50%) at near infrared wavelength. The commercial silicon APD array exhibited a fast output with rise times of 300 ps and pulse widths of 600 ps. On-chip individually filtered signals from the entire array were multiplexed onto a single fast output. NASA GSFC has tested both detectors for their potential application for space communications and ranging. We developed and compare their performances using both the 2 detected photon threshold and coincidence methods.

Photons↗
NASA NTRS2016

Low-Noise Free-Running High-Rate Photon-Counting for Space Communication and Ranging

We present performance data for low-noise free-running high-rate photon counting method for space optical communication and ranging. NASA GSFC is testing the performance of two types of novel photon-counting detectors 1) a 2x8 mercury cadmium telluride (HgCdTe) avalanche array made by DRS Inc., and a 2) a commercial 2880-element silicon avalanche photodiode (APD) array. We successfully measured real-time communication performance using both the 2 detected-photon threshold and logic AND-gate coincidence methods. Use of these methods allows mitigation of dark count, after-pulsing and background noise effects without using other method of Time Gating The HgCdTe APD array routinely demonstrated very high photon detection efficiencies (50) at near infrared wavelength. The commercial silicon APD array exhibited a fast output with rise times of 300 ps and pulse widths of 600 ps. On-chip individually filtered signals from the entire array were multiplexed onto a single fast output. NASA GSFC has tested both detectors for their potential application for space communications and ranging. We developed and compare their performances using both the 2 detected photon threshold and coincidence methods.

Photons↗
NASA NTRS2013

Per-Pixel, Dual-Counter Scheme for Optical Communications

Free space optical communications links from deep space are projected to fulfill future NASA communication requirements for 2020 and beyond. Accurate laser-beam pointing is required to achieve high data rates at low power levels.This innovation is a per-pixel processing scheme using a pair of three-state digital counters to implement acquisition and tracking of a dim laser beacon transmitted from Earth for pointing control of an interplanetary optical communications system using a focal plane array of single sensitive detectors. It shows how to implement dim beacon acquisition and tracking for an interplanetary optical transceiver with a method that is suitable for both achieving theoretical performance, as well as supporting additional functions of high data rate forward links and precision spacecraft ranging.

Farr, William H.↗
NASA NTRS2018

Use of Multi-Spectral High Repetition Rate LED Systems for High Bandwidth Underwater Optical Communications, and Communications to Surface and Aerial Systems

A variety of both existing and developing sensors would benefit from near real time communication of high bandwidth data. To cite just one example, sensors that could more accurately report real-time positions of marine mammals would be useful in reducing whale-ship collisions. Similar considerations are relevant for maritime port and harbor security, including detection and alerts for divers or autonomous underwater vehicles (AUVs) that could pose a risk to ships. Especially in ports and harbors, field experiments have confirmed that acoustic communication in these cluttered and noisy shallow water environments, compounded with vertical reflecting surfaces formed by piers and pilings, can limit the reliability and utility of underwater acoustic communications. Moreover, many sensors have greater bandwidth requirements than acoustic communications are able to provide. We here discuss the development of high repetition rate multispectral LED optical systems initially developed for imaging, but also capable of simultaneous data transmission at rates of approximately100 kilobits per second. Results are discussed for the multispectral images from coral reefs in Guam, and data transmission experiments from underwater to surface vessels. Subsequent field efforts will extend data transmission from AUVs to unmanned aircraft systems (UAS).

Underwater↗
NASA NTRS1990

Bit-error-rate testing of fiber optic data links for MMIC-based phased array antennas

The measured bit-error-rate (BER) performance of a fiber optic data link to be used in satellite communications systems is presented and discussed. In the testing, the link was measured for its ability to carry high burst rate, serial-minimum shift keyed (SMSK) digital data similar to those used in actual space communications systems. The fiber optic data link, as part of a dual-segment injection-locked RF fiber optic link system, offers a means to distribute these signals to the many radiating elements of a phased array antenna. Test procedures, experimental arrangements, and test results are presented.

Shalkhauser, K. A.↗
NASA NTRS1990

Bit error rate testing of fiber optic data links for MMIC-based phased array antennas

The measured bit-error-rate (BER) performance of a fiber optic data link to be used in satellite communications systems is presented and discussed. In the testing, the link was measured for its ability to carry high burst rate, serial-minimum shift keyed (SMSK) digital data similar to those used in actual space communications systems. The fiber optic data link, as part of a dual-segment injection-locked RF fiber optic link system, offers a means to distribute these signals to the many radiating elements of a phased array antenna. Test procedures, experimental arrangements, and test results are presented.

Shalkhauser, K. A.↗
NASA NTRS1985

An optical disk archive for a data base management system

An overview is given of a data base management system that can catalog and archive data at rates up to 50M bits/sec. Emphasis is on the laser disk system that is used for the archive. All key components in the system (3 Vax 11/780s, a SEL 32/2750, a high speed communication interface, and the optical disk) are interfaced to a 100M bits/sec 16-port fiber optic bus to achieve the high data rates. The basic data unit is an autonomous data packet. Each packet contains a primary and secondary header and can be up to a million bits in length. The data packets are recorded on the optical disk at the same time the packet headers are being used by the relational data base management software ORACLE to create a directory independent of the packet recording process. The user then interfaces to the VAX that contains the directory for a quick-look scan or retrieval of the packet(s). The total system functions are distributed between the VAX and the SEL. The optical disk unit records the data with an argon laser at 100M bits/sec from its buffer, which is interfaced to the fiber optic bus. The same laser is used in the read cycle by reducing the laser power. Additional information is given in the form of outlines, charts, and diagrams.

Thomas, Douglas T.↗
NASA NTRS1994

Pointing and tracking space mechanism for laser communication

Space optical communication is considered a promising technology regarding its high data rate and confidentiality capabilities. However, it requires today complex satellite systems involving highly accurate mechanisms. This paper aims to highlight the stringent requirements which had to be fulfilled for such a mechanism, the way an existing design has been adapted to meet these requirements, and the main technical difficulties which have been overcome thanks to extensive development tests throughout the C/D phase initiated in 1991. The expected on-orbit performance of this mechanism is also presented.

Brunschvig, A.↗
NASA NTRSDate not supplied

NASA's Current Optical Communications Efforts

NASA continues to make significant investments in optical communications technology for near Earth and deep space applications. Optical communications will enable new science and exploration missions by providing high data rates and better navigation over long distances. Small low mass terminals, even at low data rates, is also extremelty beneficial to NASA. In 2021, NASA will launch the Laser Communications Relay Demonstration (LCRD) on a Department of Defense Space Test Program satellite. LCRD consists of two optical terminals in geosynchronous (GEO) orbit and two ground stations, and it is a joint project between NASA’s Goddard Space Flight Center (GSFC), the Jet Propulsion Laboratory, California Institute of Technology (JPL), and the Massachusetts Institute of Technology Lincoln Laboratory (MIT/LL). Also in 2021, GSFC and MIT/LL will fly the TeraByte InfraRed Delivery (TBIRD) 200 Gbps Cubesat Demo in Low Earth Orbit. In 2022, JPL will launch Psyche to a unique metal asteroid orbiting the Sun between Mars and Jupiter. Psyche will carry the Deep Space Optical Communications (DSOC) payload. In 2023, NASA will do a lunar flyby with the first crewed mission of the Orion spacecraft and it will carry the MIT/LL developed Optical to Orion (O2O) payload. In addition to these flight demonstrations of optical communications, NASA is also working with civil space agencies around the world to develop international standards for optical communications via the Interagency Operations Advisory Group (IOAG) and the Consultative Committee for Space Data Systems (CCSDS).

Bernard L Edwards↗
NASA NTRS1981

Optical deep space communication via relay satellite

The possible use of an optical for high rate data transmission from a deep space vehicle to an Earth-orbiting relay satellite while RF links are envisioned for the relay to Earth link was studied. A preliminary link analysis is presented for initial sizing of optical components and power levels, in terms of achievable data rates and feasible range distances. Modulation formats are restricted to pulsed laser operation, involving bot coded and uncoded schemes. The advantage of an optical link over present RF deep space link capabilities is shown. The problems of acquisition, pointing and tracking with narrow optical beams are presented and discussed. Mathematical models of beam trackers are derived, aiding in the design of such systems for minimizing beam pointing errors. The expected orbital geometry between spacecraft and relay satellite, and its impact on beam pointing dynamics are discussed.

Gagliardi, R. M.↗
NASA NTRS1990

Brief state-of-the-art review on optical communications for the NASA ISES workshop

The current state of the art of optical communications is briefly reviewed. This review covers NASA programs, DOD and other government agency programs, commercial aerospace programs, and foreign programs. Included is a brief summary of a recent NASA workshop on optical communications. The basic conclusions from all the program reviews is that optical communications is a technology ready to be accepted but needed to be demonstrated. Probably the most advanced and sophisticated optical communications system is the Laser Intersatellite Transmission Experiment (LITE) system developed for flight on the Advanced Communications Technology Satellite (ACTS). Optical communications technology is available for the applications of data communications at data rates in the under 300 MBits/sec for nearly all applications under 2 times GEO distances. Applications for low-earth orbiter (LEO) to ground will allow data rates in the multi-GBits/sec range. Higher data rates are limited by currently available laser power. Phased array lasers offer technology which should eliminate this problem. The major problem of cloud coverage can probably be eliminated by look ahead pointing, multiple ground stations, and knowledge of weather conditions to control the pointing. Most certainly, optical communications offer a new spectral region to relieve the RF bands and very high data communications rates that will be required in less than 10 years to solve the communications problems on Earth.

Hendricks, Herbert D.↗
NASA NTRS2015

Optical Communications and Sensor Demonstration

The Optical Communications and Sensor Demonstration (OCSD) project addresses two cross-cutting capabilities of value to many future small spacecraft missions: high-speed optical transmission of data and small spacecraft proximity operations. Optical data rates demonstrated by OCSD are expected to be 200 megabits persecond (Mbs) or higher, a factor of 100 increase over current high-end CubeSat communications systems. The proximity sensors developed for this mission enable relative position measurement between two small satellites - a capability not previously demonstrated.

High-speed optical transmission of data↗