Relationship of the optical power, sensitivity, and bit errors

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Relationship of the optical power, sensitivity, and bit errors:
When the optical power is lower than the receiver sensitivity, bit errors do not necessarily occur. However, you are advised to adjust the optical power to the normal range as soon as possible.

Other related questions:
Relationship between the optical power of a line board and bit errors
Relationship between the optical power of a line board and bit errors: Bit error events may occur when the receive optical power of a line board exceeds the upper or lower threshold. If bit error events occur when the receive optical power is between the lower threshold and the upper threshold, the possible causes are as follows: The fiber quality deteriorates, the line board is faulty, or the connector is dirty.

Relationship between bit errors of a tributary board and those of an optical board
Relationship between bit errors of a tributary board and those of an optical board: 1. As the tributary board detects signals from a cross-connect board, if bit errors occur on the optical board, they will also occur on the tributary board. 2. If the optical board has no bit errors, bit errors may occur on the tributary board due to faults of the tributary board or cross-connect board. 3. If the tributary board has no bit errors, the optical board is normal and has no bit errors either.

Service bit errors
Question: What may cause service bit errors? Analysis: None Root cause: None Answer: 1. Unreasonable dispersion compensation (not enough or too much); 2. Too high or too low incident optical power; 3. Performance deterioration of the transmit laser on the OTU board at the transmit end; 4. Severely contaminated pigtail connectors; 5. Changes in fiber attenuation; 6. Performance deterioration of the receive laser on the OTU board at the receive end. Suggestion and conclusion: None

Methods for testing optical path bit errors during the acceptance of WDM devices
1. During the system commissioning of devices in back-to-back mode, use pigtails to respectively connect the Rx and Tx ports of the TQX board on the front subrack to the Tx and Rx ports of the corresponding board on the rear subrack. 2. Connect the Rx and Tx ports of the TDX board in the rear subrack at the central site to form a loopback. 3. Connect test instruments to the TI and RO ports of the TDX board on another subrack at the central site to cover most of the paths after the 24-hour bit error test. 4. If another wavelength needs to be tested, connect multiple wavelengths according to the SDH connecting method.

Definition of SDH bit error performance
Definitions of SDH bit error performance: Background block error (BBE): an errored block not occurring as a part of an SES. Errored second (ES): Errored bit second: interval of 1 second during which a given digital signal is received with one or more errored bits according to G.821. Errored block second: interval of 1 second during which a given digital signal is received with one or more errored blocks according to G0.826. Errored second: errored bit second and errored block second. Severely errored second (SES): Severely errored bit second: interval of 1 second during which a given digital signal is received with an error bit ratio greater than 1 x 10-3 according to G.821 Severely errored block second: interval of 1 second during which 30% or more errored blocks exist or at least one defect exists according to G.826. Unavailable second (UAS): Unavailable second: An unavailable period starts from the first second of 10 consecutive SES events. These 10 seconds are considered as a part of the unavailable seconds. A new available period starts from the first second of 10 consecutive non-SES events. These 10 seconds are considered as a part of the available seconds. Consecutive severely errored second (CSES): Consecutive severely errored second: 2 to 9 consecutive SES events.

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