In here, find that utilizes laser and multimode optical fiber, act as the optical signal chance fluctuation received in mechanical vibration of optic fibre, as it always goes, appear ” The modal noise ” ,So, become fiber optics telecommunication basic modes with the transmission media of the single mode fiber and light source of the laser, in the the eighties, find Model FP laser can’t keep the intersection of singlet and coherence, make in the outcoming signal having still ” The partition noise of the mould ” ,Thus make capacity and transmission distance of the optic fibre limited, working out the dynamic single longitudinal mode laser solves this problem, for instance: DFB (DFB) Laser and finer quantum well laser. These technical settlement, relay over 100km, the capacity reaches the optical communication of Gbit/s and becomes reality.

At present, the whole world employs the communication network of optic fibre extensively, the optic fibre consumption exceeds 20 millionkm, build up a fiber optic cable line of sea floor which spans Pacific Ocean, the Atlantic Ocean, see Fig. 1-2, 565Mbit/s high-speed optical fiber communication system (the transportable two-way telephones of No. 7680) in the world Has already used extensively, 2.4Gbit/s ultra high speed system put into too commercially.

At the beginning of the seventies, China had already begun the technical research of optic fibre. At the end of the seventies, produced and decayed it as 4dB/km, 1.3& mu; The optic fibre of m wavelength, and can make 0.85& mu; LED and LD and Si-APD avalanche photodiode of m, the code rate of the experimental system is 8Mbit/s.

At the beginning of the eighties, began to develop long multimode optical fiber, photoelectric detection assembly of long laser of long wave and PIN-FET of long wave. Set up short-wave length of more than 13 kilometers, long practical local line of long wave in Wuhan in 82, the code rate is 8Mbit/s and 34 Mbit/s.

At the end of the eighties, developed single mode fiber and 140Mbit/s system, set up the aerial line of monomode in Wuhan in 88, the distance is 35 kilometers.

Built up a direct buried circuit of a monomode between Hefei and Wuhu in 1991, total length 150km, from crossing over the Changjiang River under water.

Now, China has already used fiber optics telecommunication extensively, has already laid nearly 60000km optical cables so far. For instance Beijing – Wuhan – Guangzhou, national fiber optic trunk cable of Beijing – Shenyang – Harbin,etc., . China is with a vast territory, fiber optics telecommunication uses in different geography, climate environment, demand to be able to bear in the North – 40 low temperature, should resist the typhoon and be struck by lightning in the austral aerial optical fiber cable, in the northwest desert area, the optical fiber cable for direct burial wants sand blown by the wind -proof attack, in East China developed area, if has built up a high speed system of 565Mbit/s in Shanghai,etc., in Central China area such as Wuhan, have built up and stepped the circuit underwater of the Changjiang River. China has already had a fiber optics telecommunication industry of certain scale now, can produce optic fibre, optical cable, photoelectric device, optical fiber terminal and mere instrument, domestic fiber attenuation can reach 0.38 dB/km (1.3& mu; m),Its output includes that it is annual to produce about 100000km jointly, such as the factory of optical cable of Houma, flies long in Wuhan, Chengdu Siemens,etc.. China can produce the assembly of long laser of long wave, PIN-FET and nGaAs/InP-PAD that a few countries produce, life-span is reachable 200000 hours, meet the commercial requirement. The transmission code rate of the domestic optical fiber terminal reaches 140Mbit/s, 565Mbit/s (PDH system) ,Introduced the ultra high speed systems of 155Mbit/s, 622Mbit/s even 2.4Gbit/s in succession with the development of SDH technology in the 1990s, such as ” Enormous China ” (huge dragon, Datang, it hits China of Xinghe to be) Wait for national enterprises, its optical fiber terminal produced is applied to national first class trunk line, second trunk line (province grade) extensively , local network and urban telephone service. With the access network (AN) Technical maturity, China’s optical fiber communication technique will be developed more fast.

Tags: communication, Optic fibre, Routing

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