The working thory of Optical Transmitter/ Receiver

The most important optical components in opticaltransmitter is semiconductor laser, in fact, it is a laser diode (Laser Diode,LD), of course, do not use the laser diode, but the use of semiconductor lightemitting diode (Light Emitting Diode, LED).

1310nm optical transmitters generally usedirect modulation (VSB - Amplitude modulation, VSB-AM), its function is toconvert electrical signals into optical signals, the injected laser power toachieve it through an external circuit. It is set to the bias circuit toprovide the best bias power supply for the laser bias current, laser poweroutput automatic control circuit, to ensure the stability of the output opticalpower, should be designed optical power and laser temperature, such asmicrocomputer automatic control of the optical transmitter working state.

Lasers are widely used as the opticaloscillator (mamely, light-emitting devices), it is to rely on the energy stateof the laser medium material itself into the interaction with light.

To make the laser work, there must be acertain size of the current, have a certain relationship between the currentsize and light intensity, light intensity of a sharp increase when increasingthe current, this already can make the laser work, If continue to increase thethreshold current, it will form the output of the saturated zone. Thesaturation region current reaches a certain value, it will make the decline inthe quality of the transmission signal or even damage the laser diode. n termsof the optical fiber transmission power required, in the linear region severalMW of output power to meet the requirements of long-distance transmission ofsignals and information. The quality of light transmission In addition to thelight intensity the amount of spectrum and noise. Multi-wavelength spectrum ofhigh-quality analog signal transmission is not suitable, even with the thesinglemode way to work, its luminous lines width, the narrower the width of thelight waves become more pure, the more temporal coherence,good coherence oflight waves. The good coherence of light waves without using lenses and otherdevices will converge to a small point of light, but also more suitable forfiber optic incident.

The optical receiver’s main component isoptical detector which is of high sensitivity photodiode (PIN), photodiodephotoelectric effect of semiconductors to complete the detection of the opticalsignal, the optical signal to restore the RF television signal, then the RFsignalqualified RF signal amplification, and the AGC level control output afterprocessing for network distribution.

The main technologies are C/N\ C/CTB\ C/CSO. Thesethree indicators are all determined by the performance of the photoelectricconversion module. In the case of the same optical power input, convert theoutput RF level there are various sizes, high conversion efficiency ofphotovoltaic modules, its output level is high, the indicators of the C / Nvalue, and vice versa.C / N value indicators deteriorated. While the C / CSO,C, / CTB linearity of the two technical indicators by the photovoltaic modules,high-quality photovoltaic modules in the same C / CSO, C / CTB indicators, thereceived power allows a wider range.

China Telecom plans to take over the parent company of CDMA assets with more than 1200 billion RMB

According to two of YOUXIN company relevant staff's words,counted by total market share , China's third largest telecommunications provider, China Telecom (00728.HK) will announce the plans to acquire the parent company held by the CDMA network later this month, the price of materials is slightly higher than the 120 billion yuan of book value of the network.

China Telecom declares that they will seek to cope with the acquisition by debt financing ,will not consider the issue of new shares on Financing.

China Telecom Chairman Wang Xiaochu had previously said publicly that China Telecom listed company completed the acquisition of the CDMA assets of the parent company before the end of the year.

Now China Telecom is operating CDMA mobile communications by network lease. As of the end of last year, the company's total mobile subscribers 126 million, became the world's largest CDMA operators

By this news, China Telecom in the afternoon after the opening climb rise, as of 13:40, the stock was up 0.76 percent at HK $ 3.99.

Use of Optical fiber cable

Optical fiber cable is mainly madeup of light-guide fiber(as thin as a hair), theprotective plastic casing and plastic sheath. Inside the cable, there is no Gold, silver, copper and aluminum, generally no recoveryvalue. The fiber optic cableis a certain amount of optical fiber cable according to a certain heartoutsourcing jacket, and some coated layer of protection to an optical signaltransmission lines of communication. Namely: the cable by the fiber (opticaltransmission vector) formed after a certain process.

The cable is the main transfer tool fortoday's information society InformationNetwork. If the "Internet"called "information superhighway", Then, the fiber-optic network isthe cornerstone of the information highway - fiber-optic network is thephysical routing of the Internet. Once a cable is damaged and blocked in thedirection of the "information superhighway" will come to destruction.Through the optical transmission of information, information other than theaddition to the normal telephone, telegraph, fax, transmit large amounts oftelevision signals, bank transfer, stock market, a moment can not beinterrupted. At present, the transmission of long-distance telecommunicationcables by the PDH to SDH transmission rate by the original 140MB / S to 2.5GB /S, 4 x 2.5GB / S, 16 × 2.5GB / s or even higher, that is,said core one pair canbe opened 30 000 120 000 480 000 or to the development of more telephonechannels. Such a large transmissioncapacity, fiber optic cable to block not only caused huge losses to thetelecommunications sector, but due to poor communication, will give the massesthe inconvenience. For example, a computer user can not access, the stockmarket can not be known, bank exchange can not be processed, people from otherplaces can not deposit and withdraw money, all kinds of information can not betransmitted. In remote mountainous areas, once the fiber optic cable isinterrupted, it will make the county and even fiber optic cable along theseveral counties in the communication on the isolation, to be an isolated island.Losses caused to the military authorities and the people is immeasurable.

Indoor cable structure and welding considerations

Physical structure:
Indoor optical fiber cable is formed by the optical fiber(optical transmission carrier) after a certain process.
Indoor Fiber Optic Cable optical fiber (fiberglass) as thinas a hair and plastic protective casing and plastic sheath, and metals such asgold, silver, copper and aluminum in the fiber optic cable, usually norecycling value.
The indoor cable a certain number ofoptical fiber in accordance with certain cable core, outsourcing sheath, andsome coated outer sheath for optical signal transmission of a communicationline.
SpliceNotes:
A. Note the cablestripping knife depth. Cable outer sheath stripping key master jacket cutterinfeed depth fiber cut, it will easily occur. In actual operation, should edgerotation sheath cutter at the same time observe the incision, if we saw a whitepolyester tape, you should stop into the knife, remove the cutter. This step isa skilled process, required much practice to master the infeed depth.
B.fixed core beam tube fiber optic cable stripping. Cable stripping the cablefixing the cable connector box, stripping the core beam tube, do all thepreparatory work before the fiber splicing.
It should be noted at this time
1)core beam pipe can not be twisted. Before fixed cable, attention must the corebeam tube location, reinforcing member passing through the fixing screws, thestrengthening of the following items must be filled beam pipe, can not be thecore beam tube, the beam tubes of the core must be in the reinforcing memberinto the optical fiber the accommodating tray ipsilateral, can not be twistedin the reinforcing member. Reinforcement If the pressure in the beam tube ofthe core, the core of the force of the beam tube deformation caused by the lossof too much fiber core beam tube will occur due to chronic stress fracture,left hidden to the project.
2) to strengthen thelength of the piece to the right. Determined after the position of the corebeam tube can be fixed fiber optic cable. Cable fixed must not loose the fiberin the location of the connector box, to avoid due to the movement of the cableposition and lead to increased fiber loss or fiber cut problem. The fixing ofthe cable is divided into the remaining portion of the reinforcing member isfixed and cable fixation. The strengthening member fixed to pay attention toits length is too long, the fit of the connector box; too short, less than therole of the fixed fiber optic cable. Usually, when the shear reinforcementmember, should make a fixed cable splint considerable length with the distancebetween the screws of fixing the reinforcing member to the stay. The remainingportion of the cable fixed in the reinforcing member is fixed, with the screwtightening strap, which is firmly fixed in the fiber optic cable at the inletof the connector box.
3.) The core beam pipe stripping to the right length. Fixedfiber optic cable, stripping the core beam tube. Long the length of thestripping, contact to the optical fiber heat-shrinkable tube placing groove,will damage the remainder of the disc fiber fiber; stripping length is tooshort, the core bundle tubes are fixed, the fixed clamp will be stuck on thefiber, and easy to damage the optical fiber . Accordingly, it will generally beopen stripping to two fixed bayonet appropriate, without causing damage to thefiber force can be well fixed to the beam tube in the length of the core. Fixedpawl can not card too tight, otherwise the the core beam tube fiber willincrease due to power loss, the time length of the fiber will fracture, leavingthe engineering hidden.
C. fiber splice. Fiber connection directly related tothe quality and life of the project, the key lies in the preparation of thefiber end face. Fiber end face is smooth, no glitches or defects, weldingmachine well received confirmation, and can make the joints meet theengineering requirements, the fiber end face substandard welding machinerefused to work, or take out the splice loss, not in accordance withrequirements. In the process of production of fiber end face, stripping out thefiber coating, wire stripper and perpendicular to the fiber axis, wire stripperscratching Fibre; fiber is cut, the operation must be strictly in accordancewith the statutes, the use of the end face cutting knife to do the cuttinglength of the quasi-fast action, hard clever, to ensure that the optical fiberis its breaking, but not crushed; take the fiber, it is necessary to ensurethat the fiber does not touch any object to avoid end face bruised, to do so outof the end face is smooth, with a pass. The welding machine is the keyequipment for fiber splicing, is also a high level of precision and expensiveequipment. Must be strictly in accordance with the statutes in the course ofoperations, or may cause significant losses. Of particular note is theoperating procedures of the welding machine, heat shrink tubing length settingsshould be consistent and requirements.
D. I protection of fiber optic splice fiber, it is necessaryto shrink tube protection of the fiber, but also stay disk I fiber.
You should focus on:
1 The optical fiberin the process of disc fiber disc fiber bend radius is not too small, generallynot less than 4 mm. Bend radius is too small, and likely to cause refractionloss is too large and the dispersion increases. A long time, the fiber cutphenomenon may also occur.
2) when the discfiber, note the direction of the fiber distortions generally inverted"8" shaped, be careful not to wring Fibre, the plate after fiber allbelow the into the asylum disk baffle to avoid package damage optical fiber.
E. connector boxsealed cable connector box seal is very important in practical engineering.Because the surface of the optical fiber connector box water easily producemicro-cracks, the long time the fiber will fracture, and the connector box andis of directly buried way underground majority, so must do the sealing of theconnector box. The sealing of the connector box, the cable and connector box,the sealing of the two parts in the up and down between the cover of theconnector box. During fiber optic splice closure seal, the first seal at thecable sheath polished outer sheath with gauze on vertical fiber optic axialpolished, integrated more closely to the cable and sealing tape, sealing better. The seal between the upper and lower cover of the connector box, mainly Notesealing tape to prevent the seal groove in the connector box, tighten thescrews, leaving no gap evenly.

http://www.youfibercable.com/

Indoor cable structure and welding considerations

Physical structure:
Indoor optical fiber cable is formed by the optical fiber(optical transmission carrier) after a certain process.
Indoor Fiber Optic Cable optical fiber (fiberglass) as thinas a hair and plastic protective casing and plastic sheath, and metals such asgold, silver, copper and aluminum in the fiber optic cable, usually norecycling value.
The indoor cable a certain number ofoptical fiber in accordance with certain cable core, outsourcing sheath, andsome coated outer sheath for optical signal transmission of a communicationline.
SpliceNotes:
A. Note the cablestripping knife depth. Cable outer sheath stripping key master jacket cutterinfeed depth fiber cut, it will easily occur. In actual operation, should edgerotation sheath cutter at the same time observe the incision, if we saw a whitepolyester tape, you should stop into the knife, remove the cutter. This step isa skilled process, required much practice to master the infeed depth.
B.fixed core beam tube fiber optic cable stripping. Cable stripping the cablefixing the cable connector box, stripping the core beam tube, do all thepreparatory work before the fiber splicing.
It should be noted at this time
1)core beam pipe can not be twisted. Before fixed cable, attention must the corebeam tube location, reinforcing member passing through the fixing screws, thestrengthening of the following items must be filled beam pipe, can not be thecore beam tube, the beam tubes of the core must be in the reinforcing memberinto the optical fiber the accommodating tray ipsilateral, can not be twistedin the reinforcing member. Reinforcement If the pressure in the beam tube ofthe core, the core of the force of the beam tube deformation caused by the lossof too much fiber core beam tube will occur due to chronic stress fracture,left hidden to the project.
2) to strengthen thelength of the piece to the right. Determined after the position of the corebeam tube can be fixed fiber optic cable. Cable fixed must not loose the fiberin the location of the connector box, to avoid due to the movement of the cableposition and lead to increased fiber loss or fiber cut problem. The fixing ofthe cable is divided into the remaining portion of the reinforcing member isfixed and cable fixation. The strengthening member fixed to pay attention toits length is too long, the fit of the connector box; too short, less than therole of the fixed fiber optic cable. Usually, when the shear reinforcementmember, should make a fixed cable splint considerable length with the distancebetween the screws of fixing the reinforcing member to the stay. The remainingportion of the cable fixed in the reinforcing member is fixed, with the screwtightening strap, which is firmly fixed in the fiber optic cable at the inletof the connector box.
3.) The core beam pipe stripping to the right length. Fixedfiber optic cable, stripping the core beam tube. Long the length of thestripping, contact to the optical fiber heat-shrinkable tube placing groove,will damage the remainder of the disc fiber fiber; stripping length is tooshort, the core bundle tubes are fixed, the fixed clamp will be stuck on thefiber, and easy to damage the optical fiber . Accordingly, it will generally beopen stripping to two fixed bayonet appropriate, without causing damage to thefiber force can be well fixed to the beam tube in the length of the core. Fixedpawl can not card too tight, otherwise the the core beam tube fiber willincrease due to power loss, the time length of the fiber will fracture, leavingthe engineering hidden.
C. fiber splice. Fiber connection directly related tothe quality and life of the project, the key lies in the preparation of thefiber end face. Fiber end face is smooth, no glitches or defects, weldingmachine well received confirmation, and can make the joints meet theengineering requirements, the fiber end face substandard welding machinerefused to work, or take out the splice loss, not in accordance withrequirements. In the process of production of fiber end face, stripping out thefiber coating, wire stripper and perpendicular to the fiber axis, wire stripperscratching Fibre; fiber is cut, the operation must be strictly in accordancewith the statutes, the use of the end face cutting knife to do the cuttinglength of the quasi-fast action, hard clever, to ensure that the optical fiberis its breaking, but not crushed; take the fiber, it is necessary to ensurethat the fiber does not touch any object to avoid end face bruised, to do so outof the end face is smooth, with a pass. The welding machine is the keyequipment for fiber splicing, is also a high level of precision and expensiveequipment. Must be strictly in accordance with the statutes in the course ofoperations, or may cause significant losses. Of particular note is theoperating procedures of the welding machine, heat shrink tubing length settingsshould be consistent and requirements.
D. I protection of fiber optic splice fiber, it is necessaryto shrink tube protection of the fiber, but also stay disk I fiber.
You should focus on:
1 The optical fiberin the process of disc fiber disc fiber bend radius is not too small, generallynot less than 4 mm. Bend radius is too small, and likely to cause refractionloss is too large and the dispersion increases. A long time, the fiber cutphenomenon may also occur.
2) when the discfiber, note the direction of the fiber distortions generally inverted"8" shaped, be careful not to wring Fibre, the plate after fiber allbelow the into the asylum disk baffle to avoid package damage optical fiber.
E. connector boxsealed cable connector box seal is very important in practical engineering.Because the surface of the optical fiber connector box water easily producemicro-cracks, the long time the fiber will fracture, and the connector box andis of directly buried way underground majority, so must do the sealing of theconnector box. The sealing of the connector box, the cable and connector box,the sealing of the two parts in the up and down between the cover of theconnector box. During fiber optic splice closure seal, the first seal at thecable sheath polished outer sheath with gauze on vertical fiber optic axialpolished, integrated more closely to the cable and sealing tape, sealing better. The seal between the upper and lower cover of the connector box, mainly Notesealing tape to prevent the seal groove in the connector box, tighten thescrews, leaving no gap evenly.