Free-Space Laser Communication Technologies XI (Proceedings Volume)

The European Space Agency is going to conduct an inter orbit link experiment which will connect a low Earth orbiting satellite and a Geostationary satellite via optical terminals. This experiment has been called SILEX (Semiconductor Inter satellite Link Experiment). Two payloads have been built. One called PASTEL (PASsager de TELecommunication) has been embarked on the French Earth observation satellite SPOT4 which has been launched successfully in March 1998. The future European experimental data relay sat

The results from a 13.8 km horizontal laser communication (lasercom) link between the Space Technology Research Vehicle 2 (STRV-2) ground terminals are presented. These terrestrial tests are a precursor to the STRV-2 satellite-to-ground lasercom experiment scheduled to commence shortly after launch in June of 1999. Testing ground terminal performance through long terrestrial horizontal ranges (greater than 10 km) mimics the atmospheric effects of an uplink slant path to the low earth orbit (LEO) satellite.

The Optical Communications Demonstrator (OCD) is a laboratory based lasercom terminal that was developed to validate several key technologies such as precision beam pointing, high bandwidth beacon tracking and beacon acquisition. The unique architecture of OCD uses a single focal plane array (FPA) and a single fine steering mirror (FSM) for beacon acquisition, beacon tracking and point-ahead compensation. A fiber-coupled laser transmitter further reduces the complexity of the terminal. Over the last year, s

The Semi conductor Inter satellite Link EXperiment, SILEX, consists of two terminals, one terminal embarked on the French LEO observation satellite SPOT4 and one terminal embarked on the ESA GEO telecommunication satellite ARTEMIS. The objective of SILEX is first to perform optical communication experiments in orbit and then on an operational basis transmit SPOT4 earth observation data to ARTEMIS, which will relay the data to ground via its Ka band feeder link. SPOT4 with the SILEX terminal was successfully

Mountain-top to mountain-top optical link experiments have been initiated at JPL, in order to perform a systems level evaluation of optical communications. Progress made so far is reported. The NASA, JPL developed optical communications demonstrator (OCD) is used to transmit a laser signal from Strawberry Peak (SP), located in the San Bernadino mountains of California. This laser beam is received by a 0.6 m aperture telescope at JPL's Table Mountain Facility (TMF), located in Wrightwood, California. The opt

There is an upper bound on the effective size of receiving aperture for both the improvement in carrier-to-noise ratio and the reduction in signal fading of a conventional coherent detection system due to the atmospheric turbulence-induced finite transverse coherence length of the received laser field for laser radar and communications. But a coherent array detection system, which uses multiple independent apertures/receivers whose IF's are electro-optically co-phased in real time and then added, can overco

SILEX (Semi-Conductor Inter-satellite Link EXperiment) consists of one optical terminal on-board the French LEO observation satellite SPOT 4, and another on-board the European GEO telecommunication satellite ARTEMIS. While the first part of the SILEX verification plan had been oriented towards verification at equipment and subsystem levels, the final stages have mainly been devoted to terminal and system (terminals coupling effects) verification. During this final stage, a thermal vacuum test was conducted

Trade-off between Intensity Modulation Direct Detection (IM- DD) and coherent system oriented to the inter-orbit lightwave communication link is performed. Improvement in sensitivity of IM-DD system adopting high power optical fiber booster/pre- amplifiers is discussed preciously. In this paper, IM-DD system with booster/pre-amplifier and five kinds of coherent system (ASK-heterodyne, FSK-heterodyne, PSK-heterodyne, DPSK- heterodyne, and PSK-homodyne) are compared for high-data rate communication. Numerical

Although much of today's space lasercom development is concentrated in digital communications, there still remain applications where the analog lasercom link is preferred. An analog lasercom link transmits RF or IF carriers instead of decoded bits. The most important application is in commercial bent pipe satellite constellations, where modulated carriers are to be relayed between satellites, avoiding the use of costly and risky onboard demod - remod digital processors. In this paper some basic tradeoffs ar

The secure distribution of the secret random bit sequences known as 'key' material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is a new technique for secure key distribution with single-photon transmissions: Heisenberg's uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We have developed exp

A theory for the signal-to-noise ratio of optical direct detection receivers employing return-to-zero coding (and possibly optical preamplification) is developed. The results are valid for both signal-independent noise limited and signal-dependent noise limited receivers, as well as for arbitrary optical pulse shapes and receive filter characteristics, taking into account intersymbol interference. Even if the same receiver bandwidth is used, return-to-zero coding is seen to yield higher signal-to-noise rati

M-ary pulse position modulation (PPM) has received considerable attention for direct-detection photon communications over unguided channels. The analysis generally assumes that the signaling set is orthogonal. However the orthogonality of the signaling set will be destroyed by the finite area and bandwidth of optical detectors, resulting in severe intersymbol interference. This paper presents the analysis of a trellis-based pulse position modulation (T-PPM) scheme for photon communications with non-rectangu

We investigate the role of amplified spontaneous emission (ASE) produced by an optical booster amplifier at the transmitter of free-space optical communication links. In a communication terminal with a single telescope for both transmission and reception, this ASE power has to be taken into account in connection with transmit-to-receive channel isolation, especially since it partly occupies the same state of polarization and the same frequency band as the receive signal. We show that the booster ASE interce

The functional requirements and design drivers for an Optical Communications subsystem are assessed based on the system requirements imposed by a proposed Europa Orbiter mission. Unlike near-Earth optical communications systems, deep space missions impose a unique set of requirements that drives the subsystem design. Significant challenges on laser efficiency, thermal control, pointing and tracking, stray/scatter light control, and subsystem mass/power need to be addressed for a successful subsystem impleme

One of the NASA technology development programs at the Jet Propulsion Laboratory aims to increase the information return capability while reducing the size of the spacecraft via laser communications. The deep space optical transceiver developed under this program employs pulse position modulation (PPM) for both uplink and downlink transmissions. An integral part of the transceiver is the development of signal acquisition and tracking subsystem. This paper describes the baseline design of the electronic asse

Experiments were conducted to evaluate the viability of commercial-off-the-shelf (COTS) technology in the design of high-performance optical intersatellite communications links. The optical links were operated at 155, 622 and 2488 Megabits per second (Mbps) and at 1550 nm wavelength. Communications components were evaluated against performance parameters for on-off keyed (OOK) systems. Transmitters, receivers, optical amplifiers, and filters, used to minimize the impact of amplified spontaneous emission (AS

A high data rate laser transmitter assembly (LTA) has been designed as the source for an optical free-space communication link between the International Space Station and the 1-meter Optical Communication Telescope Laboratory (OCTL) to be built at the Table Mountain Facility (TMF, Wrightwood, CA). the transmitter design concept uses a fiber-based master oscillator power amplifier (MOPA) configuration with an average output power of 200 mW at a 1550 nm transmit wavelength. This transmitter source is also des

This paper presents an overview of the preliminary design of both the flight and ground systems of the Optical Communication Demonstration and High-rate Link Facility which will demonstrate optical communication from the International Space Station to ground after its deployment in October 2002. The overview of the preliminary design of the Flight System proceeds by contrasting it with the design of the laboratory- model unit, emphasizing key changes and the rationale behind the design choices. After presen

The Next Generation Space Telescope (NGST), part of NASA's Origins program, is a follow on to the Hubble Space Telescope expected to provide timely new science along with answering fundamental questions. NGST is a large diameter, infrared optimized telescope with imaging and spectrographic detectors which will be used to help study the origin of galaxies. Due to the large data NGST will collect, Goddard Space Flight Center has considered the use of optical communications for data downlink. The Optical Commu

The deployment of advanced hyperspectral imaging and other Earth sensing instruments on board Earth observing satellites is driving the demand for high-data-rate communications. Optical communications meet the required data rates with small, low-mass, and low-power communications packages. JPL, as NASA's lead center in optical communications, plans to construct a 1-m Optical Communications Telescope Laboratory (OCTL) at its Table Mountain Facility (TMF) complex in the San Gabriel Mountains of Southern Calif

Preliminary optical design and mechanical conceptual design for a 30 cm aperture transceiver are described. A common aperture is used for both transmit and receive. Special attention was given to off-axis and scattered light rejection and isolation of the receive channel from the transmit channel. Requirements, details of the design and preliminary performance analysis of the transceiver are provided.

This paper describes an extended-source spatial acquisition and tracking scheme for planetary optical communications. This scheme uses the Sun-lit Earth image as the beacon signal, which can be computed according to the current Sun-Earth-Probe angle from a pre-stored Earth image or a received snapshot taken by other Earth-orbiting satellite. Onboard the spacecraft, the reference image is correlated in the transform domain with the received image obtained from a detector array, which is assumed to have each

A wide and fine pointing mechanism (WFPM) composed of electromagnetic actuators and flexible supports has been developed for optical inter-satellite communications. It covers the whole of the scan area when it searches for the target satellite. The electromagnetic actuators, which consist of four moving-coil-type motors with long strokes, ensure a wide scan range. The flexible supports, which consist of a metal pivot and four thin springs, have vertical stiffness and rotational flexibility. Balancing the el

This paper summarizes part of a FY1998 effort on the design and development of an optical communications (Opcomm) subsystem for the Advanced Deep Space System Development (ADSSD) Project. This study was funded by the JPL X2000 program to develop an optical communications (Opcomm) subsystem for use in future planetary missions. The goal of this development effort was aimed at providing prototype hardware with the capability of performing uplink, downlink, and ranging functions from deep space distances. Such

The Optical Communications Demonstrator (OCD) is a laboratory- based lasercom demonstration terminal designed to validate several key technologies, including beacon acquisition, high bandwidth tracking, precision beam pointing, and point-ahead compensation functions. It has been under active development over the past few years. The instrument uses a CCD array detector for both spatial acquisition and high-bandwidth tracking, and a fiber coupled laser transmitter. The array detector tracking concept provides

Super compact, 3W power, 1060 nm polarization maintaining, diode-pumped ytterbium fiber amplifier with extinction ratio greater than 17 dB and wall-plug efficiency greater than 14% have been developed. Performance of the device fits requirements of free-space and satellite optical communications applications.

Master-oscillator power-amplifier (MOPA) laser systems, for future lasercom terminals to be flown in space are being developed and characterized. These lasers fall into groups for applications in deep space and near earth (including GEO) orbiting satellites. For deep space applications a diode pumped Q-switched Nd:YVO₄ oscillator and a multi-pass Nd:YAG amplifier laser with an average output power of 1.5 W and capable of supporting repetition rates of 100 KHz was studied. This lasers emits at 106

For high data rate (greater than 1 Gbps) Optical Inter- Satellite Link (OISL), a compact laser transmitter with high power and good efficiency is required. A trade-off analysis between the technologies such as the mature 840 nm laser diodes, 1064 nm diode-pumped solid state laser and the more recent 1550 nm Erbium Doped Fiber Amplifier (EDFA) is used to find the optical solution. The Si-APDs are preferred for their large detector areas and good noise figures which reduce the tracking requirements and simpli

Terrestrial fiber optic communication systems handle most of the inter-continental communication systems today. However recent studies indicate that these links, in spite of their huge bandwidth will be saturated in the near future. Hence attempts are being made is augment and may be even replace these by inter satellite links (ISLs). Though high power laser diodes have been found to be suitable for ISLs, they are unfortunately inadequate for satellite-ground links (SGL and GSL) as they are not powerful eno

A coherent array detection system can improve the heterodyne mixing efficiency compared to a conventional coherent detection system which is limited by the finite transverse coherence length of received laser field due to atmospheric turbulence for laser radar and communications. This implies a gain factor in the mean power of the IF signal from the coherent array detection system compared to the conventional coherent detection system even though the two systems receive the same power of laser signal. This

The Atmospheric Visibility Monitoring (AVM) project gathers data on the transmission of light through the atmosphere. These data are measured and collected at autonomous observatories using stellar photometric techniques. The information gathered is used to build statistical models that assess the quality of future space-to-ground optical communication links. The first of the three currently running AVM observatories became operational in 1994. Jet Propulsion Laboratory (JPL) is upgrading all three observat

The design of any optical system operating in the atmosphere requires previous investigations of atmospheric turbulence conditions at the system's location. In addition, if outdoor optical measurements are to be useful in assessing the performance of the optical system, or in checking propagation theory, they must be supported by simultaneous direct measurements of the atmospheric turbulence. Stellar observations provide a useful and convenient means for these purposes in the case of ground-satellite optica

A coherent array detection system, which uses multiple independent apertures/receivers whose IFs are electro- optically co-phased in real time and then added together, can mitigate the laser signal fluctuations and fading due to atmospheric turbulence for laser communications and radar. Thus the system performance greatly depends on the electo- optic phase-locked loops (EOPLL) used for the real time co- phase of signals from the independent aperture/receivers. But if the fast phase fluctuations due to atmos

Commercial high speed fiber optic transmitters and receivers were tested in a high energy proton environment at the Crocker Nuclear Laboratory to determine the transient impact of the space proton environment on a simulated communications link. The link was designed to simulate free-space communication between satellites. The transmit/receive bit error ratio was used as the evaluation metric. Individual electronic components on each transmitter and receiver module were tested using a variety of proton energ

Intermediate infrared Raman laser at wavelength 9.18 micrometer is generated by using Nd:YAG laser at wavelength 1.064-micrometer as a pumping source. Raman cell is filled with compressed hydrogen with an optical waveguide in it. The second order Stokes light is measured with germanium detector and its quantum conversion efficiency is 1.12%.

Given are the results of experimental study on the quasi real time holographic correction for the lens distortions in the passive observational telescope in the visible range of spectrum, using the liquid crystal optically addressed spatial light modulator.

Proposed is the novel method of dynamic nonlinear-optical correction for distortions in wide spectral band. The method is based on combining of the negative optical feedback correction and dynamic holography correction in the system, using optically addressed phase modulators. State-of-the-art of key technologies is evaluated.

Large numerical aperture telescope with nonlinear optical correction for distortions, designed for the remote self- luminous object imaging, was realized in experimental and investigated. Dynamic hologram, recorded in optically addressed liquid crystal spatial light modulator, was used as the corrector. Nearly diffraction limited performance of the system was demonstrated.