Optical fiber network transmission technology applied to expressway

The requirements for video signal transmission in highway projects have the following characteristics:

1. Large capacity: In a surveillance center, there are usually dozens or even hundreds of video signals.

2. High image quality requirements: The image requirement reaches 480 lines, the weighted SNR S/N requirement is not less than 57dB; the PAL system image requirement reaches 25 frames (50 fields/s), and the NTSC system image requirement reaches 30 frames (60 fields/ s).

3, need multi-level control: The current highway project in the video signal monitoring and management from bottom to top can be divided into the following stations, road section center, district center, provincial center four-level monitoring system.

(1) Station-level monitoring system: Each toll station needs to monitor the local video signal. (2) Central monitoring of the road section: A highway usually has one road section divided into centers to monitor and manage a certain road section.

(3) Area center monitoring system: The unified management of multiple highways is usually divided into several regions according to the geographical area.

(4) Provincial center monitoring system: Each provincial highway authority needs to conduct unified monitoring, management, and dispatch of all expressways in the province. At present, the introduction of mainstream video transmission products point-to-point video optical point-to-point video optical transceiver is currently using more common video transmission equipment (see Figure 1 for the use of schematic diagram), can be divided into analog optical transceivers and digital optical (non-compression) two. Point-to-point video optical transceiver advantages:

1. Easy to use, high video quality and good real-time performance.

2, in addition to multiple video signals can be transmitted, but also can transmit audio signals, asynchronous data, Ethernet data and other signals.

The main disadvantages of peer-to-peer video optical transceivers:

1, can not be networked, do not have protection features, poor system maintainability.

2, can not achieve long-distance transmission. If the distance is too far, only the optical link can be used. The cascade of multi-level optical transceivers will cause a sharp attenuation of the signal.