Categorized by technology

PDHOptical Transmitter
PDH (Plesiochronous Digital Hierarchy, quasi-synchronous digital series) Optical Transmitter is a 120-channel optoelectronic unity transmission equipment composed of ultra-large-scale integrated circuits, generally applied in pairs, also called point-to-point application, with the capacity of 4E1, 8E1, and 16E1; it is applicable to the small-capacity switching group network, subscriber loop network, the mobile communication (base station), private network, DDN network and so on. Its main features are: the use of ultra-large-scale integrated chip, with low power consumption and high reliability. Provides E1 remote loopback test function, easy maintenance.120 provides 4 E1 channels; has complete alarm function, can display local and remote alarms. 　Alarm information (including power-down alarm) can be reported to the opposite end through the network management channel. Adopt transceiver integrated optical device, stable and reliable performance. The whole single board design is compact and easy to use.

SDHOptical Transceiver
SDH (Synchronous Digital Hierarchy) Optical Transceiver has a large capacity, generally from 16E1 to 4032E1.

SPDH
SPDH (Synchronous Plesiochronous Digital Hierarchy) is between PDH and SDH, it is a PDH transmission system with the characteristics of SDH (Synchronous Digital Hierarchy) (based on the code speed adjustment principle of PDH, and at the same time, it adopts a part of the networking technology of SDH as far as possible). SPDH is a PDH transmission system with the characteristics of SDH (synchronous digital series) (based on the code rate adjustment principle of PDH while adopting part of the networking technology of SDH as far as possible).

Classification according to transmission signal

Analog Optical Transmitter
Analog Optical Transmitter uses PFM modulation technology to transmit image signals in real time. The analog video signal is first modulated by PFM modulation at the transmitter end and then converted to electrical-optical, the optical signal is transmitted to the receiver end and then converted to optical-electrical, and then demodulated by PFM to recover the video signal. Due to the PFM modulation technology, its transmission distance can reach 50Km or more. By using OTN/" target="_blank" >WDM technology, it is also possible to realize image and bi-directional transmission of data signals on a single optical fiber, to meet the actual needs of the monitoring project. This analog optical transceiver also has some shortcomings:
a) production debugging is more difficult;
b) a single optical fiber to achieve multi-channel image transmission is more difficult, the performance will be reduced, this analog optical transceiver can only be done on a single optical fiber to transmit a 4-channel image;
c) poor anti-interference ability, affected by environmental factors, there is a temperature drift;
d) due to the use of analog modulation and demodulation technology, the stability of its not high enough, with the increase in the time or changes in environmental characteristics, the optical transceiver is not suitable for all types of applications, but for all types of applications. increase or changes in environmental characteristics, the performance of the optical transceiver will also change, bringing some inconvenience to the engineering use.

Digital Optical Transceiver
Since digital technology has obvious advantages over traditional analog technology in many aspects, just as digital technology has replaced analog technology in many fields, the digitalization of optical transceivers is also an inevitable trend. There are two main technical ways of digital video fiber-optic converter: one is MPEG II image compression digital fiber-optic converter, the other is a full digital uncompressed video fiber-optic converter.
Image compression digital optical transmitter generally use MPEG II image compression technology, it can be compressed into an active image N × 2Mbps data stream through the standard telecom communication interface transmission or directly through the fiber optic transmission. Because of the image compression technology, it can greatly reduce the signal transmission bandwidth.
All-digital uncompressed video converter adopts all-digital uncompressed technology, so it can support any high-resolution motion and still image transmission without distortion; it overcomes the shortcomings of conventional analog FM, PM and AM converters, such as serious cross-modulation interference when transmitting multiple signals at the same time, easy to be affected by environmental disturbances, poor transmission quality, and low long-term working stability. Moreover, it supports parallel transmission of audio bidirectional, data bidirectional, switching bidirectional, Ethernet, telephone and other signals, and it is convenient for on-site wiring, plug and play. Compared with the traditional analog optical transceiver, digital optical transceiver has obvious advantages:

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