Detection of optical port LOS alarm logic module

An optical port LOS alarm is detected by combining signals from the receiver's optical power and the CDR chip to determine if the optical signal is lost, triggering an alarm when either or both indicate signal loss.

LO

S Alarm Detection Logic1.

Dual-

Signal Judgment: Modern optical modules use a combination of two signals to detect LOS: CDR Chip Output: The Clock Data Recovery (CDR) chip monitors the incoming optical signal and outputs a first LOS judgment signal based on signal integrity and timing quality. Received Optical Power: The optical receiver measures the incoming light power. This is converted into a second LOS judgment signal using a comparator to determine if the power falls below the module's sensitivity threshold.

The LO

S alarm is triggered when either the CDR-based signal or the optical power-based signal indicates a loss, improving detection accuracy and reducing false negatives. 2.

RX LOS and T

X Fault: RX LOS (Receiver Loss of Signal): Indicates insufficient optical power at the receiver, often caused by fiber contamination, misalignment, or distance exceeding the module's range.

T

X Fault (Transmit Fault): Monitors the transmitter laser for abnormal conditions, but is separate from LOS detection. 3.

Auxiliary Detection and IP

A Integration: In some network systems, such as Huawei OptiX OSN 8800, an auxiliary detection board (e.g., ST2 board) monitors LOS alarms. When a LOS is detected, the Intelligent Power Adjustment (IPA) function can automatically disable the upstream optical path to protect the network, affecting service continuity. 4.

Standards and Testing: IEEE C37. 94-compliant systems report LOS alarms in two forms: Frame-induced LOS and Signal-induced LOS, providing detailed diagnostics for troubleshooting. Far-end devices may send a Yellow (RDI) alarm to indicate received signal issues, while upstream devices may generate AIS alarms to maintain network integrity.

Key Components in LO

S DetectionCDR Chip: Shapes and recovers the electrical signal from the optical input, providing a timing-based LOS judgment. Optical Receiver (ROSA): Converts optical signals to electrical signals and measures received power. Microcontroller Unit (MCU): Integrates the LOS logic, combining CDR and optical power signals to generate alarms.

Comparator: Converts analog optical power measurements into digital LOS signals. Gold Finger Contacts: Facilitate signal transmission between the module and host system.

Practical Considerations

Ensure the optical module's sensitivity matches the link distance and fiber quality. Clean connectors and verify fiber alignment to prevent false LOS alarms. Monitor both RX LOS and TX Fault signals for comprehensive diagnostics.

In systems with IPA or auxiliary detection boards, understand that LOS alarms may trigger automatic path shutdowns affecting upstream services. By combining CDR-based signal integrity checks with optical power monitoring, LOS alarm modules provide reliable detection of signal loss, enabling rapid troubleshooting and network protection.