武汉理工大学光纤通信AB卷英文.doc

1. Multiple choice (10P each 1P)1) Which of the following codes cannot be transmitted in fiber _.A. CMI B. HDB3 C. 5B6B D. 8B1H2) A single mode fiber usually has a core diameter of _. A. 10m B. 62. 5nm C. 125nm D. 50mm3) Dispersion-shifted fiber (DSF) is a type of single-mode fiber designed to have zero dispersion near _ nm.A.1550 B.850 C.1310 D.15104) To make sure that the APD photo-detector works properly, a sufficiently _ is applied across the p-n junction. A. high forward-bias voltage B. low forward-bias voltageC. low reverse-bias voltage D. high reverse-bias voltage 5) It is well known that the total dispersion in the single-mode regime is composed of two components, _ and _ .A. mode-partition noise , inter- symbol Interference B. frequency chirp , modal dispersionC. material dispersion , waveguide dispersion D. modal dispersion , waveguide dispersion6) The mode has no cut off and ceases to exist only when the core diameter is zero.A. HE11 B. TE01 C. TM01 D. EH117) In graded-index optical fiber, the numerical aperture NA can be expressed as _.A. B. C. D.8) Which of the following doesnt belong to passive optical components _.A. Directional coupler B. Semiconductor laser C. Optical fiber connector D. Optical attenuator2. Write the full name of the following acronym （10P each 1P）1) IMD 2) SCM3) AOTF 4) RA 5) SPM 6) HFC 7) OTDM 8) TW 9) SCM 10) DBR3. Filling blanks (20P each 1P)1) The main cause of intrinsic absorption in the infrared region is ( ). 2 2) STM-1 frames provide a transmission bit rate of ( ).3) The sensitivity of a photo detector in an optical fiber communication system is describable in terms of ( ). 4) According to whether there is electric or magnetic field in the direction of propagation or not, transverse modes of light waves are classified into different 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-current noise generated in the bulk material of the photodiode, and ( ). 7) Largely due to ( ) and ( ), the optical signals undergo waveform distortion and decreased amplitude.8) The STM-1 frame is the basic transmission format for SDH. The frame lasts for ( ) microseconds; therefore there are ( ) frames per second.9) A laser consists of a ( ) inside a highly reflective ( ) as well as a means to supply energy to the gain medium.10) ( ) performance and jitter are two important indicators in a optical digital communication system.11)Optical transmitter consists of ( ), a modulator and a channel coupler.12)List two classes of transmission medium: ( ), ( ).4. Give a brief description of following terms and questions (10P each 2P)1) Stimulated Emissions2) What are the advantages and disadvantages of SDH system as compared to PDH system? 3) Gain saturation4) The disadvantage of Raman amplifier5) Dynamic range:5. Draw a block diagram of a typical optical digital communication system and briefly 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 frequency and wavelength spacing? (10P)7. In a 100-ns pulse, 6106 photons at a wavelength of 1300nm fall on an In GaAs photo detector. On the average, 5.4106 electron-hole (e-h) pairs are generated.Please calculate the quantum efficiency. (10P)8. (20P) Consider a graded-index optical fiber, core index n1=1.50 and the core cladding index difference =0.01.Try to calculate:1) The cladding index n22) The numerical aperture NA 1Multiple choice (10P each 1P) 1) B 2) A 3) A 4) D 5) C 6) A 7) C 8) B2.Write the full name of the following acronym （10P each 1P）1) IMD (intermodulation disortion)2) SCM (subcarrier multiplexing) 3) AOTF (acousto-optic tunable filter)4) RA (raman amplifier)5) SPM (self-phase modulation)6) HFC (hybrid fiber-coaxial)7) OTDM (optical time-division multiplexing)8) TW (traveling wave)9) SCM (subcarrier multiplexing)10) DBR (distributed Bragg reflector)3. Filling blanks (20P each 1P)1) the characteristic vibration frequency of atomic bonds2) 155 Mbit/s 3) the minimum detectable optical power4) TEM modes; TE modes; TM modes; hybrid modes 5) mapping; aligning; multiplexing6) surface leakage current noise 7) attenuation; dispersion 8) 125; 80009) gain medium ; optical cavityforward10) BER (The bit error rate) 11) absorption losses; scattering losses; and bending losses 12) Optical Add Drop Multiplexer(OADM) 4. Give a brief description of following questions (10P each 2P)1) Stimulated Emissions: If a photon of energy hv12 impinges on the system while the electron is still in its excited state, the electron is immediately stimulated to drop to the ground state and give off a photon of energy hv12. 2) The main limitations of PDH are: Inability to identify individual channels in a higher-order bit stream;Insufficient capacity for network management; Most PDH network management is proprietary; There is no standardized definition of PDH bit rates greater than 140 Mbit/s; and, There are different hierarchies in use around the world. Specialized interface equipment is required to interwork the two hierarchies.3)Gain saturation: when near saturation, the gain is nonlinear; saturation, the signal cannot be amplified.4) The disadvantage of Raman amplifier:Need large output power pump laser. As Raman Scattering, the energy is transferred from high frequency to low frequency. Cross talk will affect signal.5) Dynamic range: System dynamic range is the maximum optical power range to which any detector must be able to respond. 5. (10P)6. (10P)From ， obtain: ， (5P) 7. (10P)The quantum efficiency Number of e-h pairs generated h = - (6P) Number of incident photons = (4P)8. (20P)According to (2P) (1) (3P) (2) (3P)From（1）: 2 n12= n12- n 22 n22= n12（1-2） n2= n1 (4P)And: n1 =1.50，=0.01， Obtain: n2=1.50=1.50=1.500.98995=1.48491 (4P)NA = n1=1.50=1.500.14142=0.21213 (4P)武汉理工大学考试试题纸（闭卷A）课程名称光纤通信专业班级题号一二三四五六七八九十总分题分 备注: 学生不得在试题纸上答题(含填空题、选择题等客观题 1. 1. Multiple choice (10P each 1P)1) When the phase difference is an integral multiple of _, the two modes will beat and the input polarization state will be reproduced.A. 2p B. p C. 1800 D. p/22) In practical SMFs, the core diameter is just below the cutoff of the first higher-order mode，that is, for V slightly _. A. 2.4 C =3 D. =3.53) Which of the following codes cannot be transmitted in fiber _.A. CMI B. HDB3 C. 5B6B D. 8B1H4) It is well known that the total dispersion in the single-mode regime is composed of two components, _ and _ .A. mode-partition noise , inter- symbol Interference B. frequency chirp , modal dispersionC. material dispersion , waveguide dispersion D. modal dispersion , waveguide dispersion5) A single mode fiber usually has a core diameter of _. A. 10m B. 62. 5nm C. 125nm D. 50mm6) The mode has no cut off and ceases to exist only when the core diameter is zero.A. HE11 B. TE01 C. TM01 D. EH117) Which of the following doesnt belong to passive optical components _.A. Directional coupler B. Semiconductor laser C. Optical fiber connector D. Optical attenuator8) To make sure that the APD photo-detector works properly, a sufficiently _ is applied across the p-n junction. A. high forward-bias voltage B. low forward-bias voltageC. low reverse-bias voltage D. high reverse-bias voltage9) In graded-index optical fiber, the numerical aperture NA can be expressed as _.A. B. C. D.10) Dispersion-shifted fiber (DSF) is a type of single-mode fiber designed to have zero dispersion near _ nm.A.1550 B.850 C.1310 D.1510 2. Write the full name of the following acronym （10P each 1P）1) GVD 2) STS 3) ISDN 4) AWG 5) OC 6) WGA 7) GIOF 8) OTDM 9) SCM 10) DBR3. Filling blanks (20P each 1P)1) A laser is constructed from three principal parts: ( ), ( ), and ( ). 2 2) ( ) occurs because the index of refraction varies as a function of the optical wavelength.3 3) ( ) is a result of the group velocity being a function of the wavelength. 4 4) From the point of view of the wave theory, light wave could be described as an ( ).5 5) Please list three applications of EDFA in optical fiber communication system: as preamplifier of receiver、as power amplifier of transmitter and ( ).6) Attenuation in an optical fiber is caused by ( ), ( ), and ( ).7) List three applications of FBG(fiber Bragg grating): filter、( ) and dispersion compensator.8) The principal noises associated with photo detectors that have no internal gain are ( ), ( ), and ( ).9) Depending on the number of modes that a fiber can propagate, we can classify optical fibers as either ( ) or ( ).10) A typical optical digital communication system usually comprises three parts: ( ), optical fiber channel, and receiver.11) Optical transmitter consists of ( ), a modulator and a channel coupler.12) List two classes of transmission medium: ( ), ( ).4. Give a brief description of following terms and questions (10P each 2P)1) List the advantages of fiber-optic communications over other types of communication technologies.2) Differentiate between step index and graded index optical fiber 3) The Quantum Limit4) List the types of fiber attenuation and dispersion5) Dynamic range:5. Draw the element block of a Distributed forward Raman amplifier. (10P)6. Suppose two graded index fibers are misaligned with an axial offset of d=0.3a. Try to calculate the fraction of optical power coupled from the first fiber into the second fiber. （Parameter a is the core radius） (10P)7. A photodiode is constructed of GaAs, which has a band-gap energy of 1.43eV at 300K.What is the cutoff wavelength ? (10P)8. (20P) Consider a graded-index optical fiber, core index n1=1.50 and the core cladding index difference =0.01.Try to calculate:1) The cladding index n22) The numerical aperture NA 武汉理工大学教务处试题标准答案及评分标准用纸课程名称 光纤通信 （ B 卷）1Multiple choice (10P each 1P) 1) A 2) A 3) B 4) C 5) A 6) A 7) B 8) D 9) C 10) A2.Write the full name of the following acronym （10P each 1P）1) GVD (group-velocity dispersion) 2) STS (synchronous transpor signal)3) ISDN (integrated services digital network)4) AWG (arrayed-waveguide grating)5) OC (optical carrier)6) WGA (waveguide-grating router)7) GIOF (graded-index optical fiber)8) OTDM (optical time-division multiplexing)9) SCM (subcarrier multiplexing)10) DBR (distributed Bragg reflector)3. Filling blanks (20P each 1P)1) a pump source; a gain medium; an optical resonator2) Material dispersion3) Intramodal dispersion 4) electromagnetic wave 5) as the optical repeater6) absorption losses; scattering losses; and bending losses 7) Optical Add Drop Multiplexer(OADM) 8) quantum noise; dark-current noise generated in the bulk material of the photodiode; surface leakage current noise 9) single mode; multimode fiber10) transmitter 11) optical source 12) atmospheric channel (wireless); guided-wave channel (wire)4. Give a brief description of following questions (10P each 2P)1) The advantage of optical fiber communication:1、Weight and Size2、Material cost (SiO2 is plentiful)3、Information Capacity4、No electromagnetic interference5、No electrical connection6、Distance between repeaters7、Better security8、Low crosstal