1. Describe the components of optical fibers.
A: An optical fiber consists of two basic parts: a core and cladding made of transparent optical materials and a coating layer.
2. What are the basic parameters that describe the transmission characteristics of optical fiber lines?
A: including loss, dispersion, bandwidth, cutoff wavelength, mode field diameter, etc.
3. What are the causes of optical fiber attenuation?
A: Optical fiber attenuation refers to the reduction in optical power between two cross sections of an optical fiber, which is related to wavelength. The main causes of attenuation are scattering, absorption and optical loss due to connectors and connectors.
4. How is the attenuation coefficient of optical fiber defined?
A: It is defined by the attenuation per unit length of a uniform fiber in a steady state (dB/km).
5. What are insertion losses?
A: Attenuation caused by the insertion of an optical component (such as a connector or coupler) into an optical transmission line.
6. What is the bandwidth of the optical fiber related to?
A: the bandwidth of the optical fiber refers to the modulation frequency at which the amplitude of the optical power is reduced by 50% or 3dB from the amplitude of the zero frequency in the transfer function of the optical fiber. The bandwidth of an optical fiber is approximately inversely proportional to its length, and the product of the bandwidth length is a constant.
7. How many kinds of dispersion are there in optical fiber? With what?
A: Dispersion of optical fiber refers to the broadening of group delay in an optical fiber, including mode dispersion, material dispersion and structural dispersion. It depends on the characteristics of light source and optical fiber.
8. How to describe the dispersion characteristics of signal propagation in optical fiber?
Answer: it can be described by three physical quantities: pulse broadening, optical fiber bandwidth and optical fiber dispersion coefficient.
9. What is cutoff wavelength?
A: It refers to the shortest wavelength in an optical fiber that can only conduct the fundamental mode. For single-mode fibers, the cutoff wavelength must be shorter than the wavelength of the transmitted light.
10. What impact does dispersion of optical fiber have on the performance of optical fiber communication system?
A: The dispersion of the fiber will widen the optical pulse as it travels through the fiber. Affects the size of the bit error rate, and the length of the transmission distance, and the size of the system speed.
The broadening of optical pulses in optical fibers caused by different group velocities of different wavelengths in the spectral components of the light source.
11. What is backscattering?
A: Backscattering is a method of measuring attenuation along the length of an optical fiber. Most of the optical power in the fiber propagates forward, but little of it is backscattered toward the luminator. The time curve of backscattering can be observed by using the optical splitter at the luminescence device. At one end, not only the length and attenuation of the connected uniform fiber can be measured, but also the local irregularity, breakpoint and optical power loss caused by the connector and connector can be measured.
12. What is the test principle of optical time domain reflectometer (OTDR)? What function does it have?
Answer: OTDR based on the backscattering light and Fresnel reflection principle, when the use of light propagation in optical fiber attenuation of backscatter light to get information, can be used for measuring optical attenuation, splicing loss, fiber optic fault point positioning and understand the status of loss distribution along the length of optical fiber, etc., is an essential part of fiber optic cable construction, maintenance and monitoring tools. Its main parameters include dynamic range, sensitivity, resolution, measurement time and blind area.
Post time: Jun-29-2022
