Introduction: The nonlinear effect will cause additional loss and interference, deterioration of system performance. WDM high power optical system and optical fiber transmission along the long distance, therefore produce nonlinear distortion. Nonlinear distortion has stimulated scattering and nonlinear refractive index of two.
1 Introduction Optical fiber The composition.
Answer: the fiber consists of two basic components: made of transparent optical material of the core and the cladding, coating.
2 What are the basic parameters describe the transmission characteristics of optical fiber line?
Answer: including loss, bandwidth, dispersion, cut-off wavelength And the field radius.
3 reasons of fiber attenuation to what?
Answer: the loss of the fiber to reduce the optical power in the two cross section of a single fiber between, and wavelength. The main reason is the attenuation caused by scattering, absorption and the optical loss caused by the connector, connector.
4 optical fiber attenuation coefficient is defined?
Answer: use a uniform fiber attenuation in the steady state of unit length (dB/km) to define.
5 What is the insertion loss?
Answer: refers to optical transmission Insert optical components (such as line connector insertion or coupler) caused by attenuation.
6 of the bandwidth of fiber and what about?
Answer: the fiber bandwidth refers to the transfer function of the optical fiber, the optical power of the amplitude modulation frequency of 50% 3dB or less than the amplitude of zero frequency. The optical fiber bandwidth is approximately inversely proportional to its length, the length is a constant bandwidth product.
7 Some of the fiber dispersion? And what about?
Answer: fiber dispersion refers to the broadening of a single fiber group delay, including the mode dispersion and material dispersion and dispersion structure. Depending on the characteristics of the light source, optical fiber.
8 The dispersion characteristics of signal transmission in optical fiber, how to describe?
Answer: can use the pulse broadening, the bandwidth of fiber, fiber dispersion coefficient of three physical quantity to describe.
9 What is the cutoff wavelength of ?
Answer: refers to the shortest wavelength based optical fiber in the conduction mode only. For the single-mode fiber, the cutoff wavelength must be shorter than the wavelength of light transmission.
10 What impact will the performance of the fiber dispersion on optical fiber communication system?
Answer: fiber dispersion will make the process of broadening of optical pulse transmission in optical fiber. Influence of the size of the bit error rate, and transmission distance, and the size of system speed.
11 what is the backscattering method?
Answer: the backscattering method is a method of measuring the attenuation along the fiber length. Optical power in optical fiber mostly prior to transmission, but there are very few parts towards the back scattering light emitting device. Used in the light emitting device.Splitter Observe the back scattering time curve from one end, can not only measure the access of the uniform fiber length and attenuation, but also can measure the optical power loss, the irregular local breakpoints and caused in splices and connectors.
12 optical time domain reflectometer (OTDR) what is the test principle? What function?
Answer: OTDR back light scattering based on Fresnel reflection principle and production, produced by the propagation of light in fiber backscattering light attenuation to obtain information, can be used for the measurement of optical fiber attenuation, splice loss, optical fiber fault location and fiber along the length of the loss distribution is. optical cable The essential construction and maintenance and monitoring tools. The main parameters include: dynamic range, sensitivity And resolution, measurement time and area etc..
13.OTDR blind refers to what? What is the impact on the test in the actual test of area? How to deal with?
A: usually, such as movable connector, mechanical joints etc. feature points to produce a series of blind spots reflection caused by the OTDR receiver saturation caused called blind.
Blind in the fiber is divided into event two: blind and blind attenuation due to the involvement of connector caused by the reflection peak, from the starting point to the reflection peak receiver The length of the distance between the saturated peak, known as the event blind; optical fiber connector due to the intervention caused by reflection peak, from the starting point of the reflection peak to identify other events between the distance, called blind attenuation.
For OTDR, the smaller the better blind. Blind area increases with the increase of pulse width, pulse width can increase the measure length, but also increases the measuring blind area, therefore, in the measurement of optical fiber, optical fiber measurement of OTDR attachment and adjacent event points to use narrow pulse and measuring the fiber distal to use pulse width.
14 Can OTDR different types of measurements Optical fiber ?
Answer: if you use the OTDR module to single mode multimode fiber is measured, or using a multimode OTDR module such as single-mode fiber core diameter measurement 62.5mm, the measurement results of the fiber length is not affected, but such as fiber loss, optical connector loss and return loss results is not correct. So, in the measurement of optical fiber, and optical fiber. We must choose to match the OTDR measurement, so as to get the various performance indicators are the correct result.
15 common light Tester What is the 1310nm or 1550nm means?
Answer: refers to the optical signal wavelength . The use of optical fiber communication wavelength range in the near infrared region, the wavelength in 800nm ~ 1700nm. It is often divided into short wavelength band and long wavelength band, the former refers to the wavelength of 850nm, the latter refers to 1310nm and 1550nm.
16 in the current commercial optical fiber, what wavelength light has the smallest dispersion? With a minimum loss of what is the wavelength of light?
Answer: 1310nm has the minimum dispersion wavelength of light, the light of 1550nm wavelength with minimum loss.
17 according to the changes in the refractive index of optical fiber core and fiber classification?
Answer: can be divided into step optical fiber and optical fiber. Step optical fiber with narrow bandwidth, suitable for small capacity of short distance communication; optical fiber bandwidth, suitable for medium and large capacity communication.
18 According to the different modes in the transmission fiber, fiber classification?
Answer: can be divided into single-mode fiber and multimode fiber. The single-mode fiber core diameter is about 1 ~ 10 m, in the given working wavelength, only a single transmission model, suitable for large capacity and long distance communication system. Light waves can transmit multiple modes of multimode fiber, core diameter is about 50 ~ 60 m, the transmission performance than single mode optical fiber differential.
In the current differential protection of transmission multiplexing protection when installed in substation communication room photoelectricity Between the switching device and the protection device is installed in the main control room with multimode fiber.
19 Numerical aperture of step index fiber by (NA) what is the significance?
Answer: the numerical aperture (NA) said fiber light receiving ability, NA bigger, stronger ability to collect light fiber.
20 what is the birefringence in single mode fiber?
Answer: there are two orthogonal polarization modes in the single-mode fiber, when the fiber is not completely cylindrical symmetry, two orthogonal polarization modes and not degenerate, two orthogonal polarization mode index of the absolute value of the difference is the double refraction.
21 The most common optical cable There are several structures?
Answer: it is stranded and frame type two.
22 cable mainly composed by what?
Answer: is mainly composed of a fiber core, fiber sheath material, PBT ointment, (polybutylene terephthalate) material.
23 The armoured cable refers to what?
Answer: refers to the use of special cable (such as undersea cables) protection device used in the (usually steel wire or steel). Armoured are attached to the inner sheath of cable.
24 cable jacket with what material?
Answer: cable jacket or sheath usually made of polyethylene (PE) and polyvinyl chloride (PVC) material, its role is to protect the cable core is not affected by the outside world.
25 list of special cable application in power system.
Answer: there are three main kinds of special optical fiber cable:
Compound optical ground wire (OPGW), power line optical fiber is arranged in the ladle aluminum twisted structure in. Application of OPGW optical cable, played a dual function wire and communication, effectively improve the utilization rate of the power tower.
Winding cable (GWWOP), the transmission line, the cable winding or hanging on the ground.
Ssof (ADSS), high tensile ability, can be directly hung between the two seat power tower, the maximum span of up to 1000m.
26.OPGW optical cable The application of several structure?
Answer: there are: 1) the structure of plastic tube layer stranded aluminum tube; 2) structure center of plastic tube aluminum tube; 3) aluminum frame structure; 4) spiral tube structure; 5) single stainless steel tube structure (center of stainless steel tube structure, stainless steel tube stranding structure); 6) composite stainless steel tube structure (in the heart stainless steel pipe, stainless steel pipe cutter structure).
27 Stranded wire cable OPGW cable core is mainly composed of what?
Answer: AA line (Aluminum Alloy line) and AS (aluminum clad steel wire line).
28 to select OPGW cable type, which has the technical conditions should have?
Answer: 1) the nominal tensile strength of OPGW cable (RTS) (kN); 2) OPGW cable Optical fiber Core number (SM); 3) short circuit current (kA); 4) short time (s); 5) temperature range (C).
29 The bending degree of the cable is how to limit?
Answer: the cable bending radius should not be less than 20 times of cable diameter, the construction process (non static) no less than 30 times of cable diameter.
30 in ADSS cable project, the need to pay attention to what?
Answer: there are three key technologies: suspension cable mechanical design, the determination and selection and installation of fittings.
31 What are the main cable?
Answer: Cable refers to the installation of cable use hardware, mainly include: strainclamp, cgj, antivibrator etc..
32 optical fiber connector has two basic performance parameters, what are they?
Answer: commonly known as optical fiber connector joint. For the single fiber optical connector performance requirements, the focus is on the insertion loss and return loss of the two most basic performance parameters.
33 Optical fiber connector are commonly used in several categories?
Answer: according to different classification methods, optical fiber connector can be divided into different types according to the different transmission media can be divided into single-mode fiber and multimode fiber connector connector; according to the different structure can be divided into FC, SC, ST, D4, DIN, Biconic, MU, LC, MT and other types; according to the pin end face the connector can be divided into FC, PC (UPC and APC.) commonly used in fiber optic connectors: FC/PC type SC type optical fiber connector, optical fiber connector, LC type optical fiber connector.
34 in optical fiber communication system, the following common items, please point out its name.
AFC, FC Adapter ST type SC type FC/APC and FC/PC adapter adapter connector SC connector connector type ST type LC type MU jumper jumper single-mode or multimode jumpers.
35 What is the insertion loss of optical fiber connector (or insertion loss)?
Answer: is due to the connector intervention and cause effectively reduced power transmission line, for users, the smaller the value the better. ITU-T provides the value to be less than 0.5dB.
36 what is the return loss of optical fiber connector (or reflection attenuation and return loss, return loss)?
Answer: is a measure of the input power component back from the connector and bounce back along the input channel, the typical value of not less than 25dB.
37 What is the most prominent of the light emitting diodes and semiconductor laser light emitted by the difference?
Answer: the light generated by the light emitting diode is incoherent light, wide spectrum; laser produced light is coherent light, the spectrum is very narrow.
38 The light emitting diode (LED) and semiconductor laser (LD) what are the different characteristics of the most obvious?
Answer: LED LD there is no threshold, threshold, only the injected current will produce more than the laser threshold.
39 single longitudinal mode semiconductor lasers are commonly used in which two?
Answer: DFB and DBR lasers, two are distributed feedback laser, the optical feedback is provided by the distribution of optical feedback cavity Prague grating.
40 light receiver What are the main parts of two?
Answer: the main photoelectricity Diode (PIN tube) and avalanche photodiode (APD).
41 What are the factors of noise in optical fiber communication systems produced?
Answer: because of noise extinction than unqualified, the random variation of the light intensity noise, noise time jitter caused by the receiver noise and thermal noise, noise model of optical fiber, dispersion induced pulse broadening the noise generated by the LD mode distribution noise, noise frequency chirp LD noise and reflection the.
42 currently used for transmission network construction Optical fiber What are the main? What are the main features?
Answer: there are three main types, namely G.652, G.653 conventional single-mode fiber dispersion shifted single-mode fiber and G.655 non zero dispersion shifted fiber.
G.652 single mode fiber in the C band of 1530 ~ 1565nm and 1565 ~ L band 1625nm dispersion is large, generally 17 ~ 22psnm? Km, the system rate reached 2 5G Above bit/s, the need for dispersion compensation in 10G Bit/s system dispersion compensation cost is larger, it is currently in the transmission network laying one of the most common fiber.
The dispersion of G.653 dispersion shifted fiber in the C band and L band is generally -1 ~ 3.5psnm? Km, 1550nm is in the zero dispersion system, and the speed can reach 20Gbit/s 40G Bit/s is a single.wavelength The optimum fiber ultra long distance transmission. However, due to its characteristics of zero dispersion, in use DWDM There will be expansion, nonlinear effect, resulting in signal crosstalk, produces four wave mixing FWM, it is not suitable for D WDM .
G.655 NZDSF: G.655 NZDSF in dispersion of C band is 1 ~ 6psnm? Km in dispersion of L band is 6 ~ 10psnm? Km, the dispersion is small, to avoid the zero dispersion region, can suppress the four wave mixing FWM, DWDM can be used for expansion, can also open high speed system. The new G.655 fiber can be expanded to the effective area of the optical fiber 1.5 ~ 2 times, large effective area can reduce the power density, reduce the nonlinear effects of fiber.
43 what is the fiber nonlinear?
Answer: refers to when the input optical power exceeds a certain value, the refractive index of the optical fiber will be associated with nonlinear optical power, and Raman scattering and Brillouin scattering, the incident light frequency changes.
44 what is the effect on the nonlinear optical fiber transmission?
Answer: the nonlinear effect will cause additional loss and interference, deterioration of system performance. WDM high power optical system and optical fiber transmission along the long distance, therefore produce nonlinear distortion. Nonlinear distortion has stimulated scattering and nonlinear refractive index of two. The stimulated scattering Raman scattering and Brillouin scattering. More than two kinds of scattering to reduce incident light energy loss. Can be ignored in the input power is small.
45 what is the PON (passive Optical network )?
Answer: PON is a local user access network In the optical fiber loop network Based on the passive. Optical device , such as coupler, Splitter
