光纖通信_A卷英文解析

1、1. Multiple choice (10P each 1P)1) Which of the follow ing codes cannot be tran smitted in fiber.A. CMIB. HDB3C. 5B6BD. 8B1H2) A single mode fiber usually has a core diameter of.A. 10mB. 62. 5nmC. 125 nmD. 50mm3) Dispers ion-shifted fiber (DSF) is a type of sin gle-mode fiber desig ned to have zero

2、dispers ion n earnm.A.1550B.850C.1310D.15104) To make sure that the APD photo-detector works properly, a sufficie ntlyis applied across the p-njunction.A. high forward-bias voltageB. low forward-bias voltageC. low reverse-bias voltageD. high reverse-bias voltage5) It is well known that the total dis

3、persion in the single-mode regime is composed of two components,and.A. mode-partitio n no ise , inter- symbol In terfere neeB. freque ncy chirp , modal dispers ionC. material dispers ion , waveguide dispers ionD. modal dispers ion , waveguide dispers ion6) Themode has no cut off and ceases to exist

4、only whe n the core diameter is zero.A. HE11B. TE01C. TM01D. EH117) In graded-i ndex optical fiber, the nu merical aperture NA can be expressed as.1 -n2bC n 1、2也d a n1 -n28) Which of the following doesn t belong to passive optical componentsA. Directional couplerB. Semic on ductor laserC. Optical fi

5、ber conn ectorD. Optical atte nu ator2. Write the full name of the followi ng acron ym(10P each 1F)1) IMD2) SCM3) AOTF4) RA5) SPM6) HFC7) OTDM8) TW9) SCM10) DBR3. Fill ing bla nks (20P each 1P)I) The main cause of intrin sic absorpti on in the in frared regi on is ().22) STM-1 frames provide a tran

6、smissi on bit rate of ().3) The sen sitivity of a photo detector in an optical fiber com muni cati on system is describable in terms of().4) Accord ing to whether there is electric or magn etic field in the direct ion of propagati on or not,transverse modes of light waves are classified into differe

7、nt types:(),(),()and ().5) Please list three steps of SDH Multiplexing:(),(),().6) The principal noises associated with photo detectors that have no internal gain are quantum noise,dark-curre nt no ise gen erated in the bulk material of the photodiode, and ().7) Largely due to () and (), the optical

8、 sig nals un dergo waveform distorti on anddecreased amplitude.8) The STM-1 frame is the basic transmission format for SDH. The frame lasts for ()microsec on ds; therefore there are () frames per sec ond.9) A laser con sists of a () in side a highly reflective () as well as a means to supplyen ergy

9、to the gain medium.10) () performa nee and jitter are two importa nt in dicators in a optical digital com muni cati onsystem.II) Optical tran smitter con sists of (), a modulator and a cha nnel coupler.12) List two classes of tran smissi on medium:(),().4. Give a brief description of following terms

10、 and questions (10P each 2P)1) Stimulated Emissi ons2) What are the adva ntages and disadva ntages of SDH system as compared to PDH system?3) Gain saturati on4) The disadvantage of Raman amplifier5) Dyn amic ran ge:5. Draw a block diagram of a typical optical digital com muni catio n system and brie

11、fly describe the functions of each part. (10P)6. A GaAs laser operating at 800nm has a 500- m length and a refractive index n=3.7.What are the freque ncy and wavele ngth spaci ng? (10P)67. In a 100-ns pulse, 610 photons at a wavelength of 1300nm fall on an In GaAs photo detector. On the6average, 5.4

12、 10 electr on-hole (e-h) pairs are gen erated.Please calculate the qua ntum efficie ncy. (10P)8. (20P) Consider a graded-index optical fiber, core index n 1=1.50 and the core cladding index difference A=0.01.Try to calculate:1) The cladding index n 22) The nu merical aperture NA1. Multiple choice (1

13、0P each 1P)1) B 2) A3) A 4) D 5) C6) A 7) C8) B2. Write the full name of the followi ng acro nym (10P each 1F)1)IMD(in termodulati on disorti on)2)SCM(subcarrier multiplex ing)3)AOTF(acousto-optic tun able filter)4)RA(rama n amplifier)5)SFM(self-phase modulatio n)6)HFC(hybrid fiber-coaxial)7)OTDM(op

14、tical time-divisi on multiplex ing)8)TW(traveli ng wave)9)SCM(subcarrier multiplex ing)10)DBR(distributed Bragg reflector)3. Fill ing bla nks (20F each 1F)1) the characteristic vibrati on freque ncy of atomic bonds2) 155 Mbit/s3) the minimum detectable optical power4) TEM modes; TE modes; TM modes;

15、hybrid modes5) mapp ing; alig ning; multiplex ing6) surface leakage curre nt no ise7) atte nuati on; dispers ion8) 125 ; 80009) gain medium ; optical cavityforward10) BER (The bit error rate)11) absorptio n losses; scatteri ng losses; and bending losses12) Optical Add Drop Multiplexer(OADM)4. Give a

16、 brief descripti on of follow ing questi ons (10F each 2F)1) Stimulated Emissi ons: If a phot on of en ergy hv 12 imp in ges on the system while the electro n is still in its excited state, the electr on is immediately stimulated to drop to the ground state and give off a phot on of en ergy hV12.2)

17、The main limitati ons of FDH are:In ability to ide ntify in dividual cha nn els in a higher-order bit stream;In sufficie nt capacity for n etwork man ageme nt;Most FDH n etwork man ageme nt is proprietary;There is no sta ndardized defi niti on of FDH bit rates greater tha n 140 Mbit/s; and.There are

18、 differe nt hierarchies in use around the world. Specialized in terface equipme nt is required to in terwork the two hierarchies.3) Ga in saturati on: whe n n ear saturati on, the gain is non li near; saturati on, the sig nal cannot be amplified.4) The disadva ntage of Rama n amplifier:Need large output power pump laser. As Rama n Scatteri ng, the en ergy is tran sferred from high freque ncy to low freque ncy. Cross talk will affect sig nal.5) Dyn amic