Views:0 Author:Site Editor Publish Time: 2021-06-22 Origin:Site
Compared with electrical interconnection, optical interconnection has many advantages, such as high speed, high bandwidth, low loss, anti-interference and so on. It has attracted more and more attention in the field of short distance communication, and gradually replaced electrical interconnection as the main transmission mode of the communication system. As the core module of the optical interconnection system, the main function of the optical receiver is to convert the optical signal transmitted by the line into electrical signal, and extract the original signal after amplification, judgment and other processing.
Here is the content list:
What are the components of the outdoor optical receiver?
What is the classification of outdoor optical receivers?
What are the Specifications of the Outdoor Optical Receiver?
The optical receiver is a machine that receives the optical signal transmitted from the optical fiber and converts it into the electrical signal for amplification. The construction of a complete optical receiver can be roughly divided into three parts.
The first part is a photodetector. The main function of the photodetector is to use the photoelectric effect to transform optical signal into an electrical signal, and the basic principle of its detection process is optical absorption. In the optical communication system, the requirements for photodetectors are high sensitivity, fast response, low noise, low cost and high reliability.
The second part is the optical receiving system. The components of the optical receiving system are usually placed at the receiving end, and the function of receiving antenna is to collect and gather the light field propagating in space to the detector surface.
The last part is signal processing. In space optical communication systems, the signal received by the optical receiver is very weak, and in the case of high background noise field interference, the signal-to-noise ratio of the receiver will be low, so signal processing is very necessary. The components of this part generally include preamplifier, main amplifier, equalizer, decider, decoding circuit and so on.
According to the type of modulation signal, the optical receiver can be divided into an analog optical receiver and a digital optical receiver. The modulation signal of an analog optical receiver is an analog signal, which has the characteristics of simple equipment, and is usually used to transmit video signal in radio and television system. The modulated signal of the analog optical receiver is an analog signal, which is characterized by simple equipment and is usually used for transmitting video signals in broadcasting and television systems.
Generally speaking, detectors for optical fiber communication need low dark current, high responsivity and cutoff frequency. Currently, there are three kinds of detector structures, which are PIN, APD and MSM. Therefore, the optical receiver can be divided into PIN-HBT, MSM-HEMT, PIN-FET and PIN-HEMT according to their photoelectric integration.
According to different classification methods, optical receivers can be divided into other types.
The specifications of optical receiver are mainly based on its main technical parameters. The products produced by different manufacturers should strictly abide by the industry principles formulated by the state. The main technical parameters of optical receiver include sensitivity, responsivity, amplitude frequency characteristics, noise and nonlinear distortion.
The sensitivity of the optical receiver is defined as the minimum optical power level that the optical receiver can detect. The sensitivity of AM optical receiver commonly used in optical fiber CATV system is -9dBm. But when such a small photoelectric level input, the carrier to noise ratio of the output signal is too low, so the general input photoelectric level should be -2 to -3dBm.
The response of the optical receiver is defined as the average optical current output from the photodiode by the unit optical power received by the optical receiver. The response of PIN photodiode used in cable TV system is greater than 0.85 A/W.
3. Amplitude frequency characteristics
The amplitude frequency characteristic of an optical receiver is defined as the gain fluctuation within a specified bandwidth. The gain fluctuation of optical receiver used in general CATV system is less than ± 0.5 dB in the range of 40-550 MHz.
The noise of the optical receiver includes quantum noise caused by the randomness of electron hole pair excited by photon, noise caused by dark current and thermal noise in circuit. The quantum noise current is related to quantum conversion efficiency, incident light power and circuit bandwidth. In the fiber-optic cable TV system without optical amplifier, the carrier to noise ratio is mainly determined by the relative intensity noise Rin of the optical transmitter, quantum noise and thermal noise of the receiver. When the received optical power is low, the quantum noise and thermal noise of the optical receiver play a major role. However, with the increase of the received optical power, the relative intensity noise of the optical transmitter will become the main source of noise, and the thermal noise of the optical receiver is much more serious than its quantum noise.
5. Nonlinear distortion
Because the optical receiver works in low level and small signal state, its nonlinear distortion is negligible compared with the optical transmitter.
With the continuous development of fiber Bragg grating technology and the rapid progress of integrated circuit design level, the design and development of optical communication optical receiver is expected to be further expanded in many aspects. Hengchi Electronic Equipment Co., Ltd. has been committed to producing products that can stably serve optical fiber communication projects for 15 years since its establishment, and has been highly praised. If you are engaged in the outdoor optical receiver industry, you can consider our high quality products.