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1. What is the blind spot of OTDR? What is the impact on testing? How to deal with the dead zone in the actual test?Typically, a series of blind spots caused by saturation of an OTDR receiver is called a blind spot.The dead zone in the fiber can be divided into the event dead zone and the attenuation dead zone: the distance from the starting point of the reflection peak caused by the interference of the active connector to the receiver saturation peak is called the event dead zone; from the starting point of the reflection peak to the active connector in the fiber The distance from the point at which other events due to interference can be identified is called the attenuation dead zoneFor OTDR, the smaller the dead zone, the better. As the pulse width increases, the dead zone increases. While increasing the pulse width increases the measurement length, it also increases the measurement dead zone. Therefore, when testing optical fibers, narrow pulses should be used for the measurement of the OTDR and its adjacent event points, and wide pulses should be used for the measurement of the far end of the optical fiber.2. Can OTDR measure different types of fibers?If a single-mode OTDR module is used to measure a multi-mode fiber, or a multi-mode OTDR module is used to measure a single-mode fiber with a core diameter of 62.5mm, the measurement results of the fiber length are not affected, but the results such as fiber loss, optical connector loss and return loss Incorrect. Therefore, when measuring optical fibers, it is necessary to select an OTDR that matches the measured optical fiber for measurement, so as to obtain the correct results of various performance indicators.3. What does "1310nm" or "1550nm" mean in ordinary optical test instruments?It refers to the wavelength of an optical signal. The wavelength range of optical fiber communication is in the near-infrared region, with wavelengths between 800nm and 1700nm. It is usually divided into short-band and long-band, the former refers to the 850nm wavelength, and the latter refers to the 1310nm and 1550nm wavelengths.4. Which wavelength of light has the least chromatic dispersion in current commercial fibers? What wavelength has the least loss of light?The 1310nm wavelength has the smallest optical dispersion and the 1550nm wavelength has the smallest optical loss.5. How to classify the fiber according to the change of the refractive index of the fiber core?Divided into stepped fibers and gradient fibers. The stepped fiber has a narrow bandwidth and is suitable for short-distance communication with small capacity; the tapered fiber has a wide bandwidth and is suitable for large and medium-capacity communication.6. How to classify fibers according to the different modes of light wave transmission in fibers?Divided into single-mode fiber and multi-mode fiber. The core diameter of a single-mode fiber is about 1-10 μM, and at a given wavelength, only one fundamental mode is transmitted, which is suitable for large-capacity long-distance communication systems. Multimode fiber can transmit multimode light waves, and its core diameter is about 50-60 μM, and its transmission performance is worse than that of single mode fiber. When transmitting the current differential protection of multiple protection, multi-mode optical fiber is used between the photoelectric conversion device in the communication room of the substation and the protection device in the main control room.7. What is the meaning of numerical aperture (NA) of step index fiber?The Numerical Aperture (NA) represents the light-gathering ability of the fiber. The larger the NA, the stronger the light-gathering ability of the fiber.Fiber hope fiber optic cable and patch cord manufacturers can provide high-quality fiber optic cables, fiber pigtails, fiber patch cords, single-mode multi-mode fiber, welcome to inquiry!

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1. What is the bandwidth of optical fiber related to?The bandwidth of the fiber refers to the modulation frequency when the amplitude of the optical power is 50% or 3dB lower than the amplitude of the zero frequency in the transfer function of the fiber. The bandwidth of an optical fiber is approximately inversely proportional to its length, and the product of the bandwidth length is a constant.2. What is the dispersion of optical fibers?Different frequency components or different mode components of the optical signal (pulse) transmitted in the fiber propagate at different speeds, and will inevitably produce signal distortion (pulse broadening) after reaching a certain distance. The generation of optical fiber dispersion is based on two factors. One is that the optical signal entering the optical fiber is not monochromatic light (the light emitted by the light source is not monochromatic or the modulated signal has a certain bandwidth); the other is the dispersion effect of the optical fiber on the optical signal. .3. How to describe the dispersion characteristics of signal propagation in optical fibers?It can be described by pulse broadening, fiber bandwidth and fiber dispersion coefficient.4. What is the cutoff wavelength?It means that a single-mode fiber usually has a certain wavelength. When the transmitted light wavelength exceeds this wavelength, the fiber can only propagate light in one mode (fundamental mode), and under this wavelength, the fiber can propagate multiple modes ( light containing higher-order modes).5. What effect does the dispersion of optical fiber have on the performance of optical fiber communication system?The dispersion of the fiber will broaden the transmission of the light pulse in the fiber. Affects bit error rate, transmission distance and system rate.6. What is backscatter?Backscattering is a method of measuring attenuation along the length of the fiber. Most of the optical power in the fiber is forward propagating, but there is also a small amount of optical power that is scattered back toward the illuminator. The time curve of backscattering can be observed using a beamsplitter. Starting at one end, it is possible to measure not only the length and attenuation of a uniform fiber, but also local irregularities, breaks and optical power loss at splices and connectors.7. What is the testing principle of OTDR? What is the function?OTDR is made according to the principle of backscattering and Fresnel reflection of light. It uses the backscattered light that is produced when light propagates in an optical fiber to obtain attenuation information. It can be used to measure the attenuation of the fiber, splice loss, the location of the fiber failure point, and understand the loss distribution along the fiber length. It is an indispensable tool in fiber optic cable construction, maintenance and monitoring. Its main parameters include: dynamic range, sensitivity, resolution, measurement time and dead zone.Fiber hope fiber optic cable and patch cord manufacturers can provide high-quality fiber optic cables,fiber pigtails, fiber patch cords, single-mode multi-mode fiber, welcome to inquiry!

Optical fiber is the abbreviation of optical fiber. It is a fiber made of glass or plastic. It can transmit optical signals to thousands of kilometers away. Hundreds of thousands of optical fibers are combined together to make a cable-like optical cable. , so the optical cable is composed of a certain number of optical fibers, and the outer sheath is wrapped with a protective layer, which not only improves the strength of the optical fiber, but also greatly increases the communication capacity.Fiber optic cables are widely used, and the application scenarios are roughly as follows:A. Backbone transmission network (SDH/SONET), such as submarine optical cables between major cities and ocean bottoms, etc.;B. Ethernet (Ethernet), including the current fiber to the home (FTTH), to the building (FTTB), to the community, etc., mainly our home and office networks;C. Data network (Fiber Channel), various storage devices, databases, including the developing cloud computing service system;D. Cable TV transmission (PIN reception);E. Other special purpose transmissions, such as fighter jets, ships.The following are 43 common questions and knowledge points about fiber optic cables:1. The basic structure of optical fiberThe bare fiber is generally divided into three layers, the central high-refractive-index glass core (the core diameter is generally 50 or 62.5μm), the middle is the low-refractive-index silica glass cladding (the diameter is generally 125μm), and the outermost is the resin coating for reinforcement. Floor. Optical fiber is the abbreviation of optical fiber. It is a fiber made of glass or plastic. It can be used as a light transmission tool. The transmission principle is "total reflection of light".2. What are the basic parameters of the transmission characteristics of optical fiber lines?Including loss, dispersion, bandwidth, cutoff wavelength, mode field diameter, etc.3. What are the main factors of fiber attenuation?The main factors that cause fiber attenuation are: intrinsic, bending, extrusion, magazines, non-uniformity, and butt joints.Intrinsic: It is the inherent loss of the fiber, including: Rayleigh scattering, intrinsic absorption, etc.Bending: When the fiber is bent, part of the light in the fiber will be lost due to scattering, resulting in loss.Squeeze: Loss caused by tiny bends in an optical fiber when it is squeezed.Impurities: Losses caused by impurities in the fiber absorbing and scattering light propagating in the fiber.Non-uniformity: Loss caused by non-uniform refractive index of the fiber material.Docking: The loss generated when the optical fiber is docked, such as: different axes (the coaxiality of single-mode fiber is required to be less than 0.8μm), the end face is not perpendicular to the axis, the end face is not flat, the butt core diameter does not match and the welding quality is poor.4. How is the attenuation coefficient defined?Defined by the attenuation (dB/km) per unit length of a uniform fiber in steady state5. What is insertion loss?Refers to the attenuation caused by the insertion of optical components such as connectors or couplers in optical transmission lines.Fiber hope fiber optic cable and patch cord manufacturers can provide high-quality fiber optic cables,fiber pigtails, fiber patch cords, single-mode multi-mode fiber, welcome to inquiry!