Optical transceiver, is light signal transmission terminal equipment. Because the present technical enhancement, fiber prices drop make it in various fields to obtain the very good applications so each optical transceiver manufacturer is like a are mushrooming developed. But here the manufacturer most technology is not fully mature, develop new technology need cost and human, material etc, thus producing manufacturer is much is the medium and small enterprises, each brand also successively appeared.
In a remote optical fiber transmission, cable of the signal transmission effect is small, optical fiber transmission system transmission quality mainly depends on the quality of the optical transceiver, because optical transceiver responsible for photoelectric conversion and light emitting light receiving, its disadvantages directly affect the entire system, therefore need many new users or to interested users optical transceiver performance and application to understand somewhat, can better configuration and purchasing.
Optical transceiver species
Optical transceiver from interface classification should be video optical transceiver, optical transceiver, audio data optical transceiver, Ethernet optical transceiver
Optical transceiver points three categories: PDH, SPDH, SDH.
Plesiochronous Digital Hierarchy, PDH (quasi synchronous Digital series) optical transceiver is small capacity optical transceiver, general is applied in pairs, also called point-to-point applications, the capacity is commonly 4E1, 8E1, 16E1.
SDH (Digital Synchronous Hierarchy, Synchronous Digital series) optical transceiver capacity is big, general is 16E1 to 4032E1.
Plesiochronous Synchronous Digital Hierarchy (SPDH) optical transceiver, between PDH and SDH between. SPDH is with SDH (synchronous digital series) characteristics of transmission system (based on the PDH PDH code speed adjustment principle, at the same time, use as far as possible some of SDH network technology).
Monitor term word, that is video optical transceiver, transmission video primarily and other data, audio, switch quantity, Ethernet telephone signals of the photoelectric conversion transmission equipment, he is the essence of: photoelectric conversion transmission equipment, On both ends of the fiber optic cable, one receiver sniper, just as its name implies optical transceiver, So broadly, based on optical fiber network for transmission signal photoelectric conversion equipment can be called optical transceiver.
This classification used for telecom on transmission signals (also has compressed video) compression optical transceiver and monitors and radio and TV industry of incompressible of video optical transceiver.
summary
Usually say of optical transceiver is transmission video of incompressible optical transceiver.
Video optical transceiver development in China is accompanied by monitoring development began, video optical transceiver is put 1 to multiple video signal through simulation of varied coding convert light signals through the optical fiber transmission medium to the equipment, divide again for analog optical transceiver and digital optical transceiver.
1, analog optical transceiver
Analog optical transceiver used PFM modulation technology, real-time transmission image signal. Launch the video signal first conducts simulation PFM modulation, and then carry on electricity - light conversion, light signals to the receiver, light - electricity conversion, and then PFM demodulation, recovering the video signal. As a result of the PFM modulation technology, the transmission distance can achieve 50Km or farther. By using WDM technology, still can be in a single fiber implemented on images and data signals bidirectional, meet the actual demand of monitoring project. The analog optical transceiver also exist some disadvantages:
A) production debugging is difficult,
B) single fiber realize multiple image transmission is difficult, performance will decline, at present the analog optical transceiver generally can only do single fiber transmitted on 4 road image;
C) anti-interference ability is poor, by environmental factor influence is bigger, have WenPiao;
D) due to use is simulated demodulation technology and its stability is not quite high, with use time increases or environmental characteristic changing, optical transceiver performance also can produce change, to project USES brought some inconvenience.
2, digital optical transceiver
As a result of digital technology and traditional analog technology compared in a lot of respects has obvious advantages, so as the digital technology in many fields as replaced the simulation technology, optical transceiver digitization is an inevitable trend. At present, digital video optical transceiver basically has two kinds: one kind is technical method MPEG II image compression digital optical transceiver, another kind is full digital incompressible video optical transceiver.
Image compression digital optical transceiver usually adopts the MPEG II image compression technology, it will be moving image compression into N * 2Mbps data flow over standard telecommunication communication interface transmission or directly through the optical fiber transmission. As a result of the image compression technology, it can greatly reduce signal transmission bandwidth.
Digital incompressible video optical transceiver adopts full digital without compression technology, therefore can support any high resolution movement, still images without distortion transmission; To overcome the conventional analog FM, phase-modulation, an amplitude optical transceiver multi -channel signal transmit simultaneously into adjustable interference when seriously, easily influenced by environmental disturbance effect, transmission inferior quality, long working stability not higher shortcomings. And supports audio two-way, data bidirectional and switch quantity bidirectional and Ethernet, telephone and other signal concurrent transmission, field wiring convenient, plug and play.
Digital light end machine has obvious advantages
With traditional analog optical transceiver, compared to digital light end machine has obvious advantages:
1) transmission distance is long: can reach 80Km, even farther (120Km);
2) support video nondestructive decode-and-forward relaying, therefore can use multilevel transmission mode;
3) by environmental interference is lesser, transmission quality;
4) support signal capacity up to 16 road, even more (32 road, 64 road).
Second, optical transceiver from analog to digital
From in the late 1980s analog optical transceiver application, to begin to enter Chinese since 2001 digital optical transceiver appear; Deduced economic development impetus scientific and technological progress and scientific and technological promoting economic development process.
The earliest analog optical end machine if using simulated FM, amplitude, phase-modulation ways of putting the video, audio, baseband signal modulation data etc transmission to a load items, through the other end of the receiving optical transceiver were demodulated, back into a corresponding baseband video, audio and data signals.
The signal modulation to light, through video transmission, optical fiber were often use the following modulation mode:
AM or stressed FMT system (AM) : full simulation system, optical transmission unit inside light emitting diode (LED) brightness or intensity with the input video amplitude linear change. The light signal amplitude sent via fiber-optic light receiving units, by its signals are converted to analog baseband video.
FM or pulse frequency modulation (FM) : be also a simulation system, radiofrequency modulated video signal linear through input of frequency modulation, after adjusting the carrier and with light transmission unit LED or laser emitter, after the frequency modulation signal sent via fiber-optic light receiving units, by its signals are converted to analog baseband video.
AM video transmission is widely used in industrial safety on the market from low to the CCTV surveillance and safety in applications. Applicable to 5.5 km (350 miles) or more short transmission, such a system can provide the qualitative video performance is good, and always can achieve 250C long-distance transmission rs-five the quality requirements. But AM video transmission equipment only suitable for 850nm. Multimode operating wavelength this limits the biggest usable transmission distance. The more notable is, for every 1dB optical path loss is concerned, an amplitude system based on the SNR of linear correlation attenuation for 2dB, therefore, acceptable video transmission quality can only in a relatively short distance gain cable. Some manufacturers equipment may be in initial installation stage requires receiver gain adjustment so that complicate the installation process. Lastly, AM products reach today ITS application in the industrial safety and high-end required the rs-five medium distance video transmission 250C technical requirements.
FM video transmission is has widely applied in ITS industrial safety and high-end market transmission mode. Can provide high quality video transmission performance, usually can achieve rs-five 250C mid-range transmission quality requirements and cost more reasonable. Unlike AM equipment, FM product applies to 1330nm. Multimode or single-mode operation, and 1550nm. Single-mode operation, its typical applications of transmission distance is up to 66 km (42 miles) {customer needs can reach 80KM}. Without for convenient installation requiring users to adjust. Although FM means to be able to provide high quality transmission, but the signal-to-noise ratio in higher levels of light attenuation, and the longer the transmission distance of optical transmission process will decay, and signal-to-noise ratio and optical attenuation is no longer a linear relationship between, thus its performance is not completely predict or remain the same.
In addition, it is difficult to reach the system based on FM rs-five 250C short transmission technology requirement, and FM video emitting and receiving unit are also vulnerable to external electromagnetic sources and cellular phone and mobile phones from the radio interference (EMI/RFI), usually in the field or roadside environment. By technology restriction, optical transceiver include one way or double road, road 4, 8 video and bring PTZ control data of optical transceiver, in a core transmitted on realizing point-to-point, transmission capacity for serious shortage of optical fiber transmission capacity with sufficient wasted, complex, large capacity and high points equipment requires more core transmission; Add video technology simulation the defects of the vulnerable to bring the characteristics of interference, easy to decay, realize the multilevel relay, cascade is more difficult, transmission business of simplification (usually only video and data signals), video transmission using the simulation CWDM also had the technical conditions and WDM device expensive the limitations in optic fiber and optical transmission equipment in many industries and expensive even have definite demand also us1,400 for its application. The multiple signals with preach caused crosstalk.
In site monitoring applications, users may have many different signals, such as video images, audio, data, Ethernet, telephone or other user defined signal, in order to enhance the efficiency in the use of optical fiber, cost reduction, must the various signal for reuse in optical transceiver, so in a pair of or a root optical fiber transport. For FM, amplitude, phase-modulation optical transceiver speaking, video, audio, will be multiplexed or data signal mixed FM, amplitude, phase-modulation in a carrier on will inevitably lead to various mirror, hand in adjustable interference. So on the market at present thering is no lack of many famous foreign brands FM, amplitude, phase-modulation optical transceiver multiple video, audio and data with preach occurs when the mutual interference phenomenon, these unstable phenomena are simulated modulation technology has long been inherent shortcoming.
Digital optical transceiver transmit digital signals, carried easily high-capacity reuse and that there would be no mutual interference. For growing market demand, analog optical transceiver already can not adapt to the large capacity and more business (video, data, audio, switch quantity, Ethernet, interphone, phone etc) transmission requirements, multi-channel crosstalk, easy attenuation, aging, after-sales service trouble problems such as analog optical transceiver makes gradually with the emergence of new technology, market and application to down.
Digital optical transceiver appear solved analog optical transceiver that's problems. Starting in 2000 in communications technology development makes light transmission devices technique and digital video technology development, the digital optical transceiver began to move towards the market and industry applications. Along with the digital optical transceiver and analog optical transceiver of contrast development, slowly digital optical transceiver gradually began to replace analog optical transceiver, so far, has already formed the analog optical transceiver and digital optical transceiver 28 minutes the world situation. Believe in the near future analog optical transceiver can only become monitoring in the history of a noun. If the early analog optical transceiver is foreign optical transceiver manufacturers to bring the earliest transfer market, then the digital optical transceiver be domestic and foreign competing power, domestic manufacturers advantages and foreign manufacturers of a process.
The latest generation of video transmission equipment by optical fiber transmission units inside one model - several converter or digital signal encoder (encoder/decoder), for the input analog baseband signal (from CCTV video camera, video, audio and data switch quantity, Ethernet, etc.) adopting digital decoding technology for processing. Then a digital signal and modulation to the LED or laser emitter, through the optical fiber transmission to the light receiving unit, here the previous digital signal is an internal several - mode converter back into analog baseband video signal. So, the system in electric completely transparent will light emitter's video input through the optical fiber to send to the light receiving unit video output, and can directly matching are currently using NTSC and PAL or SECAM CCTV cameras.
Can say, analog signal digitize again after the transmitting optical transceiver technology is a qualitative leap development. Digital optical transceiver solved analog optical transceiver transmission capacity, less business capability, less signal easy attenuation, easy crosstalk, advantages disadvantages such as highlights: transmission capacity, business types, single fiber transmission capacity can reach dozens of road hundreds of road incompressible video, transmission of business are diversified transmission video, audio, data, Ethernet, telephone signal, switch quantity, etc. Various kinds of signals. This saves fiber, and also improves the utilization rate of optical fiber bandwidth, improving the cost-effective, The signal quality of ascending to a higher level, the signal-to-noise ratio of the video images in 10bit coded 67 ~ next can achieve 70db, far outstripping the distance under 50 ~ of the analog signal 60db specifications. In the cascade technology application is handy in analog optical transceiver.
When we talk about the digital decipher video transmission equipment, evaluation of performance between product and product needed to consider the performance parameters is system used by digital digits. Digital digits fundamentally defines the electrical system dynamic range and end-to-end signal-to-noise ratio, and video transmission performance is the main influencing factors. Now any resolution for the six system technically is backward, does not represent the highest technology level, at present this system must generate images on visible unnatural signals, and video attenuation. In view of this, in a digital decipher video transmission system which used in bits at least should be 8 bits. 8-bit resolution or decoding ability can make video transmission quality meet or exceed the rs-five 250C short transmission or real video transmission quality requirements.
Adopting digital incompressible technology, digital video coding technology 10 (10bit) and 15Mhz sampling frequency technology makes the digital video digitizing process sample point says more accurately, obtained image effect more lifelike, more perfect.
Third, optical transceiver the transmission distance
The transmission distance refers to optical transceiver actual could be transmitted light signals the maximum distance. This is a nominal value, it depends on the equipment and the actual environment factors, double fiber of optical transceiver can be generally transmission, single fiber 120KM from 1 to the general transfer 1 to 80KM.
Optical transceiver appear now phone optical transceiver, its purpose is through the optical fiber to transmit voice call the optical transmission equipment, equipment available through a pair of optical transmission 1-720 road telephone, long-distance transmission telephone, shielding room, telephone supermarket, the residential quarters FangHao best choice.
Four, optical transceiver interface type
Optical transceiver typical physical interface is as follows:
BNC interface
BNC interface refers to coaxial cable interface, BNC interface for 75 uefa coaxial cable connection with, provide charge (RX), hair (TX) two channels, which is used for non-equilibrium signal connection.
Fiber interface
Fiber interface is used for connecting optical fiber cable physical interface. There are usually SC, ST, FC etc several types, they by Japanese NTT company development. FC is the abbreviation of Ferrule by, its external strengthen way is using metal sleeve, tighten way for LuoSiKou. ST interface 10Base - F, commonly used in SC interface 100Base - FX commonly used in.
RJ - 45 interface
RJ - 45 interface is Ethernet is most commonly used interface, RJ - 45 is a popular name means by IEC (60) 603-7 standardization, use by international connectors standard definition of 8 position (8 needles) of modularization socket or plugs.
RS - 232 interface
RS - 232 - C interface (also called EIA rs-five 232 - C) is the most commonly used one kind of serial communication interface. It is in 1970 the us-based electronic industries association (EIA) joint bell system, modem manufacturer and computer terminals manufacturer shall be jointly formulated for serial communication standards. Its full name is "data a DTE or DCE can send across data communication equipment between serial binary data exchange interface technology standard". This standard adopts a 25 feet DB25 connectors, for each of the pin connector of signal content codes, the level of various signal codes. (currently multi-purpose DB9)
RJ - 11 interface
RJ - 11 interface is we say at ordinary times phone line interface. RJ - 11 is used for Western electronics company (room) the development of Western connector generic name. Its appearance is defined as 6 needle connecting device. Formerly named WExW here, the x says "active", contacts or lineup needle. For example, WE6W has all six contacts, Numbers 1 to 6, WE4W interface using only four needles, the two outside contacts (1 and 6) no, WE2W use only two needle (i.e. telephone interface with)
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