International leading quantum cryptography communication technology with interference immunity

1. Stability: Realized complete disturbance immunity of line 0-1KHz

This scheme performs excellent in optical cable tests, such as test for embedded optical fiber, aerial optical cable, river-crossing railway bridge optical cable and so on, which is the core technology in dealing with complex optical fiber link environment.

Field test for aerial optical cable of electric power
Electric test site in Chanping, Beijing	polarization disturbance caused by breeze	system stability
Test result：disturbance immunity of line 0-1KHz; category 1-12 strong and weak disturbance can be resisted, almost no disturbance to ±800KV high voltage.

Test on Wuhu Yangtze River Bridge both for highway and railroad
Image of Wuhu Yangtze River Bridge	Test result on duct optical cable stability of Wuhu Yangtze River Railroad Bridge
Test result on duct optical cable stability of Wuhu Yangtze River Railroad Bridge: Testing environment: The total length of the communication line is 69.7km, among with the length for the duct optical cable crossing Wuhu Yangtze River Railroad Bridge is 10.6km;      Testing time：＞ 5000 hours；      testing result: bit error of useful signal secularly stabled below 2%;      Security: unidirectional transmission technology and active phase modulation technology.

　

2. Summary on actual securities of quantum cryptography

• There is always security issues in any actual system, so does quantum cryptography;
• The security flaws of receiving terminal is bigger than transmitting terminal;
• The security of reciprocating system is obviously weak than unidirectional system;
• In principle, security of single detector system is strong than double detector system;
• single laser is more secure than multi-laser;
• Active device is more secure than passive device.