Fiber optic technology and its military applications

Abroad, research and development of military applications of fiber optic technology culminated in the mid-1980s. In the 1990s, these research and development activities were further strengthened. This article summarizes the latest foreign advances in the military application of optical fiber technology and several new optical fiber technologies with military application prospects.

1 Introduction

As a transmission medium, optical fiber has a series of obvious advantages compared with traditional copper cables. Therefore, since the 1970s, optical fiber technology has not only achieved rapid development in civil fields such as telecommunications, but also because of its resistance to electromagnetic interference, Good confidentiality, resistance to nuclear radiation and other advantages, as well as the advantages of light weight and small size, make it also received the attention and favor of the governments and military of various developed countries.

Especially in the United States, as early as the mid-1980s, there were about 400 optical fiber military application projects planned. These projects included fixed facility communication networks, tactical communication systems, remote-controlled reconnaissance vehicles and aircraft, fiber-guided missiles, and avionics data buses. And control links, shipboard fiber optic data bus, anti-submarine warfare network, underwater acoustic towed array, remote control deep submersibles, sensors and nuclear tests, etc. These projects have reported successively that different progress has been made.

Since the 1990s, the military application of optical fiber technology has continued to be valued by the military of the United States, Europe and other countries. In the United States, the planned projects of the three military fiber optic technology development activities are divided into five major parts: active and passive optical components, sensors, radiation effects, point-to-point systems, and network systems. Organized by the three armed forces fiber optic coordination committee, the annual investment is 50 million US dollars.

Facing the 21st century, the US Department of Defense has listed "photonics, optoelectronics" and "point-to-point communication" as two of the top ten defense technologies in 2010. Among them, fiber optic technology occupies a decisive position. This indicates that the United States and other Western countries will conduct comprehensive research on the military application of optical fiber technology and accelerate it. The preliminary application, demonstration and verification indicate. In the 21st century, military communications and weapons and equipment will not be "modernized" or "advanced" without optical fiber technology, and will be passively beaten in future wars.

2 Military applications of fiber optic technology

2.1 Land-based military applications of fiber optic technology

2.1.1 Military communication application of optical fiber technology

The application of optical fiber technology in land-based military communications mainly includes three aspects: 1) a remote system for strategic and tactical communications; 2) a local area network for inter-base communication; 3) links between facilities such as satellite earth stations and radars.

Since the emergence of the "information superhighway" concept, the United States has led the world in the development of military information superhighways. In June 1992, the joint meeting of the US chiefs of staff issued a framework document called "Samurai C4T" on the US military's 21st century communications and cooperative operations master plan. The goal of the "Samurai C4T" plan is to establish a global real-time military communication network, called the "information sphere", according to the requirements of the military "information highway". It will be a command network that connects soldiers, command posts and various sensors, and is a sensitive C8 system. Its basic network is the National Defense Information System Network (DISN), which is composed of military and civilian communications systems on the ground and satellites.

The target DISN is a broadband integrated service digital network (B-ISDN) with a transmission capacity of up to several Gb / s. It is planned to be implemented in three stages of near, middle and far, and it will take 10-15 years to realize it from 1995.

The Battlefield Information System (BIS-2020) is the future Army information system that supports the US Army ’s 21st century combat theory.

As an Army Tactical Command and Control System (ATCCS) supporting the "BIS-2020" system, it is mainly a geographical

Decentralized, highly mobile, and dense communication systems. It will also be implemented in three steps. The third step ATCCS, the final

The target system is the "BIS-2020" system, and its development period is from 1995 to 2000. And fiber optic LAN, especially

Fiber optic distributed data interface (FDDI) is one of the key technologies.

The C3 system of the US military played an important role in winning the war in the Gulf War. In particular, the United States Three Armed Forces Joint Tactical Communication System (TRI-TAC), Mobile Switching Equipment (MSE) and the improved Army Tactical Communication System have all played important roles. However, these systems also exposed many problems. Therefore, the US military made technical improvements to TRI-TAC in three aspects based on these problems and future operational requirements. One is the TAC-1 optical cable system in charge of the Air Force. It will replace the coaxial cable and equip the US TRI-TAC system distributed around the world. The second is the Army ’s Field Optical Cable Transmission System (FOTS). It is planned to replace the CX-11230 coaxial cable with 10000km of optical cable; the third is to connect the digital exchange and radio equipment by the Marine Corps Field Optical Cable System (FOCS). In addition, the local distribution system is also an integral part of TRI-TAC. It will mainly replace four 26-pair CX-4566 type cables between field communication vehicles with field optical cables. In addition, the US Navy and Air Force are also building their own broadband optical fiber communication networks using asynchronous transfer mode (ATM).

The Air Force's C3I system is one of the largest applications of fiber optic technology in the US Air Force. In 1979, the US GTE company obtained a US $ 325 million contract for the MX missile launch site C3 system from the US Air Force. The optical cable was used as the interconnection line between the combat control center, regional support center, missile shelter and maintenance facilities. The total length of the line was 15,000 km , Connecting more than 5,000 computers in 4,800 manned and unattended locations. In the ten years from 1987 to 1996, the investment budget of the MX missile C3 system reached 517 million US dollars.

The US military also put forward the idea of ​​deploying dual links of military satellites and optical cables in the main military doorway, in order to take advantage of the complementarity of the working characteristics and performance characteristics of the two communication methods to ensure the invulnerability of strategic and tactical integrated communications in crisis situations.

2.1.2 Application of optical fiber technology in radar and microwave systems

Due to the inherent advantages of low optical fiber transmission loss and frequency bandwidth, the application of optical fiber in radar systems is first used to connect the radar antenna and the radar control center, so that the distance between the two can be expanded from 300m to 2 ~ 5km. Using optical fiber as the transmission medium, its frequency band can cover the X-band (8 ~ 12.4GHz) or Ku-band (12.4 ~ 18GHZ). At present, X-band high-frequency fiber optic systems have been put into practical use, and Ku-band broadband microwave fiber-optic line systems have also been reported extensively. The application of optical fiber in microwave signal processing is mainly optical fiber delay line signal processing. Advanced high-resolution radar requires delay devices with low loss and large time-bandwidth products for signal processing. The traditional coaxial delay line, surface acoustic wave (SAW) delay line, charge coupled device (CCD), etc. can no longer meet the requirements. Although magnetostatic wave devices and superconducting delay lines can meet the technical requirements, they are still far from being practical. Optical fiber delay line has the advantages of low loss (in the range of 1 ～ 10GHz, the loss per unit delay time is only O.4 ～ O.1dB / ps), the time bandwidth product is large (up to 104 ～ 106), and the bandwidth is wide (> 10GHz). And, the dynamic range is large, the signal of the three-time transition is small, it is quite easy to realize the delay line tracking each other, and it can be packaged into a small package box. Most of the signal processing used for phased array radar is a delay line composed of multimode fiber. At present, foreign optical fiber delay lines have entered a mature period. In order to increase the flexibility of phased array radar antenna beam scanning, reduce initial power consumption, and precisely control the phase and amplitude of elements required to achieve low spatial side lobes, it is necessary to provide beam (phase) control signals for each antenna element , Polarization control signal and amplitude control signal. The use of optical fiber to transmit these control signals at high speed and good phase stability can greatly reduce the amount of electronic components of each active unit, simplify the system configuration, reduce radar cost, and reduce volume and quality. The application of fiber optic technology in phased array radar also includes the phase shift required for beamforming in optically controlled phased array radar with fiber delay lines. In the electro-optical phased array transmitter, integrated optics is used for beam forming, and fiber optic technology is used for flexible remote control of the antenna. Broadband fiber real-time delay phased array receiver using fiber dispersion prism technology. Among them, in addition to optical fiber delay lines, advanced optical fiber component technologies such as optical fiber couplers, wavelength division multiplexing / demultiplexers, integrated optics, polarization-maintaining optical fibers, high-dispersion optical fibers, optical fiber amplifiers, and optical fiber gratings have been applied.

2.1.3 Fiber Optic Guided Missile (FOG-M)

The concept of fiber-guided missiles was proposed in 1972, but its development was in the early 1980s. The US Army's projects are mainly used for anti-tank and anti-helicopter helicopters. The range of the early design was only 10km. The US Navy's projects are mainly used for air-to-air, air-to-ground and ship-to-ship operations. The US Army spent about US $ 100 million on FOG-M development from 1989 to 1991. More than 40 ignition tests were carried out, and the project was cancelled in 1991 due to the high development cost. During the Gulf War, when the US military used light weapons against heavy weapons or armored formations, it realized that it needed a light and heavy emergency weapon that could expand and maintain the lethality required to attack the armored formations, and FOG-M could meet this extremely powerful The need for lethality, survival rate, highly deployable and flexible systems. In order to provide the Army Quick Response Force with a means to deal with long-range helicopters and tanks, the United States resumed the development of FOG-M. It is planned to enter the stage of demonstration and verification in early 1994.

Low-speed production began in the fiscal year 1997-1998.

Recently, it has been reported that the US Army Missile Command is conducting a technical demonstration of a long-range fiber-guided missile that can hit a moving target 100 km away. FOG-M is not only valued by the US military, Germany has also carried out development and research, and has obtained cooperation from France. Italy has also joined it. The three countries have jointly formulated the Trilateral Optical Fiber Missile (TRIFOM) plan. Among them, Polypheme 20 is used to deal with division-level armored vehicles and helicopters, and can be installed on light or high motor vehicles with a range of 15km; Polypheme 60 is used to kill fixed or low mobility targets with a specific depth, with a range of 60km; Polypheme SM It is used for launching submarine underwater hundreds of meters deep, anti-helicopter or aircraft, the range is 10km. At the European Ship Expo held in Paris in October 1996, the French Aerospace Missile Division exhibited the newly developed fiber-guided multi-purpose shipborne missile.

Brazil also exhibited a FOG-M with a range of 20km at the Paris Air Show in 1995.

2.1.4 Fiber Optic Tether Weapon

The U.S. military military robots have begun mass production in 1988, with an average annual output value of 500 million US dollars. Fiber Optic Remote Controlled Vehicle (TOV) is a highly mobile multi-purpose wheeled vehicle that is tethered to a base station trailer with an optical cable. It can send various reconnaissance devices, sensors and weapons to dangerous war zones to perform such tasks as reconnaissance and mine detection. , Mine clearance, obstacle removal and ammunition supply tasks, the vehicle speed can reach 3.5km / h, and the operating distance can reach 15-30km. For example, a fiber-optic tethered vehicle called Ranger (ranger) developed by Grumman successfully hit an armored target 300m away in the test. Its top speed is 27km per hour. The Remote Control Aircraft (AROD), jointly developed by the US Naval Ocean System Center (NOSC) and the Sandia National Research Institute, is a ducted fan-type device tethered with fiber optics. It carries out reconnaissance missions through television. AROD III has a range of 4000m.

The balloon-borne radar reconnaissance system using the tethered optical cable has also been rapidly developed. The balloon has a height of 600m to 6000m, a payload of 100kg to 2000kg, and a stagnation time of 15 to 30 days. It can function like an altitude warning aircraft. Fiber optic remote control underwater submersible (ROV), also known as underwater robot or unmanned submarine, is available in towed and tethered types. By being equipped with different equipment, it can carry out topographical surveying, survey and salvage of wrecks and sea crashes, rescue submarines, deployment of anti-submarine listening devices, detection and removal of mines, autonomous mine laying and underwater bait. Eagle-type electronic bait is a fiber-optic tethered unmanned aerial vehicle developed by the US Naval Research Laboratory. It weighs 36 kg, uses a rotary wing, and has a load capacity of 6.5 kg. The final test is planned to be completed in 1997.

2.1.5 Application in underground nuclear tests

Because optical fiber has two major advantages in the nuclear environment, one is not affected by electromagnetic pulses, and the other is that the optical fiber can be recovered within a few seconds after being exposed to a strong radiation weapon explosion. Therefore, the US military used fiber optic technology in underground nuclear tests.

2.1.6 Application in night vision devices

According to reports, the US military added fiber optic components to the new night vision device to enhance the image. This optical fiber component is mainly an optical fiber fusion panel.

2.2 Maritime military applications of fiber optic technology

2.2.1 Shipborne high-speed optical fiber network

Because modern ships are equipped with a large number of electronic equipment such as communications, radar, navigation, sensor systems and weapon command systems, plus other electrical equipment, serious electromagnetic interference and radio frequency interference have been caused. For this reason, in the early 1980s, the United States The Navy implemented a plan to develop a large-scale new ship's optical fiber regional network as a computer data bus-the AEGIS (Yusdun) plan. In early 1986, the US Naval Marine System Command established SAFENET (Resistant Adaptive Fiber Embedded Network) Committee on this basis. And in 1987, a working group was established to guide the formulation of SAFENET-I and SAFENE one or two sets of standards. They were completed in January 1991 and January 1992, respectively. The former is a military enhanced IEEE802.5 token ring network with a transmission rate of 16Mb / S, and the latter is based on ANSI 3XT9.5 FDDI (Fiber Distribution Data Interface) token cup network with a transmission rate of 100Mb / s. These systems have been installed on ships such as the CG-47 Aegis missile cruiser, DDG 51-class missile destroyer, and the USS George Washington. The U.S. Marine System Command and the Defense Advanced Research Projects Agency have also jointly developed standards for the development of high-speed optical network (HSON) prototypes using synchronous optical network (Sonet), broadband integrated service network (B-ISDN) and asynchronous transmission mode (ATM) The plan, developed and evaluated by the Naval Research Laboratory (NRL), will last for three years from mid-1991. The network uses single-mode fiber, the transmission rate from 155Mb / S (OC-3) to 2.4Gb / S (OC-48). In 1992, the first phase of 1.7Gb / S was achieved. The transmission capacity of the radar data bus on the USS Little Rock carrier reached 1Gb / S, and the original coaxial cable weighing 90 tons was replaced by a half-ton single-mode optical cable.

SUBACS-Submarine Advanced Combat System (SUBACS-Submarine Advanced Combat System), SUBACS is the US Navy ’s largest shipborne underwater optical fiber communication program project, the project is planned in all Los Angeles muscle 688 attack nuclear submarines and the new "Trident" trajectory The missile submarine is equipped with an optical fiber data bus, which connects the sensors and fire control system to the distributed computer network, thereby greatly improving the submarine's data processing capability. This is called AN / BSY-1. According to reports, the research and development expenditure for the first two years of the entire plan is 638 million US dollars, and the production contract is expected to be at least 2 billion US dollars. Later, in the "Sea Wolf" SSN-21 class attack submarine produced after 1989, the AN / BSY-2 integrated optical fiber combat control acoustic system developed by the General Electric Company's Naval Warfare Department was used.

In November 1997, the United States completed the installation of optical fiber using air-sending optical fiber technology on the nuclear-powered aircraft carrier Truman (CYN75). Later, it was successfully laid on the "Enterprise Number" (CVN 65). It is also planned to lay fiber optic systems using air-fed fiber technology on the "Reagan" (CVN 76), "Nimitz" (CVN68) and "USSWasp" (LHD-1). Among them, the optical fiber used on "Trumen" reaches 67.58km.

2.2.2 Fiber optic hydrophone system

Optical fiber hydrophone is a device that uses optical fiber technology to detect underwater acoustic waves. Compared with traditional piezoelectric hydrophones, it has extremely high sensitivity, large enough dynamic range, essential anti-electromagnetic interference ability, and no impedance matching requirements. The advantages of light weight and arbitrary structure of the “wet end” of the system are enough to meet the challenges from the continuous improvement of the submarine noise suppression technology, adapt to the requirements of the anti-submarine strategy of various developed countries, and are regarded as one of the key defense technology development projects.

The main military applications of fiber optic hydrophones are:

· All fiber optic hydrophone drag array

· All-fiber submarine sound monitoring system (Ariaden project)

· Conformal hydrophone array of all-fiber light submarine and surface ship

· Ultra low frequency fiber optic gradient hydrophone

· Marine environmental noise and quiet submarine noise measurement

Research on this technology in the United States began in the late 1970s, and more than $ 100 million in research and development funds were invested in the 1992 fiscal year. The U.S. Naval Research Laboratory (NRL), Naval Underwater Equipment Center (NUWC), Gould ’s Maritime Systems Branch, and Litton Guidance and Control have jointly developed an all-fiber hydrophone towed array (AOTA), submarines, and surface ships Various anti-submarine applications such as conformal hydrophone array (LWPA) sea trial systems have reached a state where they can be deployed after extensive marine trials. They are currently developing large-scale (hundreds of units) all-fiber hydrophone array systems and related technologies. In the past ten years, the United States has tested various applications of all-fiber hydrophones and their arrays, and the test results have been very successful. The British research on hydrophones is mainly undertaken by Plessey Defense Research Branch, Naval Systems Branch and Marconi Underwater Systems Co., Ltd., and has developed various anti-submarine applications such as all-fiber hydrophone towed arrays, submarine sound monitoring systems, etc. The sea trial system has also carried out a series of sea trials.

2.2.3 Fiber Optic Guided Torpedo

Like fiber-guided missiles, fiber-guided torpedoes can greatly improve torpedo attack performance. The fiber-guided torpedo tested by the US Naval Marine System Center has a guidance distance of 5km and a speed of 18 knots (33km / h). Further tests will reach 70 knots (130km / h), and the range will be expanded to 100km. The key is the fiber optic cable and its pay-off technology and advanced fiber optic hydrophone. France has also conducted a successful fiber-guided torpedo test, the guidance distance reached 20km.

2.2.4 Mast photoelectric observation device

Since the 1980s, periscope manufacturers in the United States, Britain, Germany and other countries have begun to develop a multi-function sensor imaging system that does not penetrate the pressure hull of the submarine, that is, the submarine photoelectric mast, which will be used to replace the traditional periscope and device. A new type of submarine that entered service in the mid and late 1990s and early 2000s. The self-protected combined photoelectric periscope system used by the four avant-garde class ballistic missile nuclear submarines built by the British Navy in the 1990s consists of a photoelectric mast and an optical periscope. The photoelectric mast's rotatable multi-sensor head and inboard control The information between the stations is transmitted by the optical cable. This mast-type photoelectric observation device has also been used in armored vehicles and helicopters.

2.3 Aerospace military applications of fiber optic technology

The application of optical fiber technology in the aviation field mainly has the following four aspects:

· Replace copper wire for point-to-point optical fiber data transmission

· For interconnection of high-speed network and computer

· Used for flight and engine control, so-called "light-controlled flight"

· Smart structure and smart skin

2.3.1 Point-to-point data transmission and network application

The point-to-point links that have been used in small amounts in aircraft are mainly used for data transmission between avionics "black boxes". These links perform well in F / A-18, AV-88 and Blackhawk helicopters, with data rates from 10Mb / s to 100Mb / s. Due to the relatively high price of optical fiber system, low loss and wide-band capacity can not be fully utilized, so the number of equipment is small, only used for occasions with serious electromagnetic interference and electromagnetic pulse problems. As the complexity increases, the bandwidth of the fiber optic data bus will also increase. For example, F-22 and RAH-66 Comanche require 100Mb / s ～ 1Gb / s high-speed optical fiber data bus for communication and sensor interface.

2.3.2 Flight-by-Light

Because electromagnetic interference (EMI), electromagnetic pulse (EMP), high-intensity radio frequency (HIRE), and new threats (such as direct energy weapons) can seriously threaten the flight safety of aircraft equipped with electronically controlled flights, people have to take appropriate Shielding measures, but this will cause an increase in weight, and light-controlled flight can play the role of two birds with one stone. For tactical aircraft, if light-controlled flight is used instead of electronically controlled flight, the weight can be saved by about 90-317kg. Moreover, the fiber optic system can not only be used for flight control, but also be used to control and monitor the subsystems of the aircraft. It is also very important in "stealth" aircraft, because the noise radiation of the cables in the aircraft for several kilometers will become the radiation source and be easily discovered by the radar. The use of fiber optic systems does not have this problem. The development of light-controlled flight began in 1980 with the US Army ’s "Advanced Digital Light Control System (ADOCS) program, undertaken by Boeing Vertol Co., and was successfully installed on the Sikorski UH-60A" Black Hawk "helicopter. The demonstration is planned. It is intended to be installed on various military helicopters. In 1985, NASA and the Department of Defense began a plan for the "Fiber Optic Control System Assembly (FOCSI)". The plan was in 1993. In the fall, an open loop flight test was conducted on the US Navy ’s F-18 fighter, focusing on flight control sensors, as well as sensors for total pressure, static pressure, Mach number, angle of attack, and for a complete integrated propulsion / Sensors for the overall temperature required by the flight control system.

NASA is also preparing for another demonstration of fiber-controlled flight in an "OPMIS" program. The American Advanced Research Projects Agency (ARPA) and NAS have embarked on a light-controlled flight plan. This plan is called the "Light Control Flight Advanced System Hardware Technology Reinvestment Project (FLASH)" and is implemented by Wright Laboratories.

2.3.3 Application of fiber optic technology in missiles and space vehicles

In addition to the fiber link used for the MX missile launch site described earlier, fiber can replace cables in the three subsystems of the launch vehicle and greatly improve the reliability of the launch vehicle. The three subsystems are: 1) take-off countdown (TO) umbilical system; 2) avionics internet; 3) monitoring sensors. According to reports, the European Space Agency (ESA) signed a contract with the British company Sira to require the company to design a low-cost, passive and highly flexible fiber optic monitoring system for the spacecraft to solve the lack of visual data, especially incomplete The question is unfolded and is intended to be installed on the ENVISAT spacecraft scheduled for launch at the end of 1998, and to be assembled on all spacecraft after standardization. Rockwell International of the United States has studied the feasibility of the application of optical fiber technology in the instrumentation and control of liquid fuel rocket engines. Applications include: fiber optic pyrometers for turbine blade temperature measurement; fiber optic Raman temperature sensing during the combustion process; fiber optic deflectometer measurements for turbine pump bearing wear, etc.