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FANUC Controller
Servo/Axis · Advanced · 45-120 minutes
Fanuc Alarm 5135 - FSSB: ERROR MODE
Alarm 5135 indicates the FSSB (Fiber Servo System Bus) communication network has entered error mode due to compromised data integrity between the CNC and servo amplifiers. This is typically caused by physical damage to fiber optic cables, contaminated optical connectors, amplifier hardware faults, or cascaded communication errors across the FSSB loop. The CNC detects excessive communication retries or signal loss and halts operation to prevent unpredictable axis behavior.
5135
Fanuc Alarm 5135 - FSSB: ERROR MODE
SYSTEM ALARM 5135
Fanuc alarm 5135: SYSTEM ALARM 5135. This alarm indicates a fault condition detected by the Fanuc control. Refer to the alarm number and name to identify the specific system or function involved.
Root Cause Summary
Alarm 5135 indicates the FSSB (Fiber Servo System Bus) communication network has entered error mode due to compromised data integrity between the CNC and servo amplifiers. This is typically caused by physical damage to fiber optic cables, contaminated optical connectors, amplifier hardware faults, or cascaded communication errors across the FSSB loop. The CNC detects excessive communication retries or signal loss and halts operation to prevent unpredictable axis behavior.
Causes and Fixes
- 1
Power down the system. Inspect all FSSB fiber optic cables between CNC (JD1A/JD1B on control) through each αi/βi servo amplifier in the loop for visible damage, excessive bending, or pinch points. Check that orange protective caps are present when disconnected.
Never look directly into active fiber optic connectors - laser radiation can cause eye damage.
- 2
Disconnect each fiber connector at both CNC and amplifier ends. Clean all optical connectors using lint-free optical swabs and isopropyl alcohol (IPA 99%+). Inspect ferrule end faces with optical scope for scratches or contamination. Replace any damaged cables.
Use only Fanuc-approved fiber optic cables (A660-8006-T series). Incorrect cable types will cause communication errors.
- 3
Reconnect all FSSB cables ensuring positive click engagement. Power on and check amplifier LED status: green LED solid indicates normal FSSB communication. Navigate to SYSTEM > DIAGNOSIS > #900-919 (FSSB monitor) to verify communication status for each axis shows '0' (normal).
- 4
If alarm persists, use FSSB loop-back test: disconnect fiber from last amplifier in chain, install loop-back connector, and observe if alarm clears. Systematically move loop-back toward CNC to isolate failing amplifier or cable segment.
Call a technician if:
- ·Multiple amplifiers show hardware failure
- ·CNC FSSB master board replacement needed
- ·Optical fiber infrastructure damage
Prevention
- Regular optical fiber inspection and cleaning
- Protect fiber cables from mechanical damage
- Monitor FSSB error counters in preventive maintenance
- Maintain parameter backups
Common Mistakes
- Forcing optical connectors causing damage
- Not checking FSSB address sequence
- Ignoring intermittent communication errors
- Replacing cables without cleaning connectors first
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