1. Executive Summary
| Port Identifier | MCH-1-3 (Port 3) |
| Link Designation | FTTH feeder — mixed build |
| Alarm Trigger | 2026-02-15 18:49:31 UTC+8 |
| Report Generated | 2026-02-16 12:37:00 UTC+8 |
| Investigation Status | ACTIVE FAILURE |
| Severity Classification | CRITICAL |
| Failure Type | FIBER BREAK at 5.0 km (±50 m) |
| Required Action | DISPATCH FIELD CREW IMMEDIATELY |
| Estimated Repair Time | 4–8 hours (cable repair / emergency splice) |
Summary: A complete fiber break was detected on Port MCH-1-3 (FTTH feeder — mixed build)
at approximately 5.0 km from the ALM port. The alarm was triggered on 2026-02-15 at 18:49:31
when the link loss exceeded the configured threshold, registering a total loss of 100.00 dB (sentinel value
indicating complete signal loss). The automatic fault analysis identified the break point at 5,000 m with a
fault loss of 93.86 dB. A confirmation OTDR shot and a full high-accuracy measurement both verified the
failure. The break is located on the feeder section between the ODF/patch-panel (150 m) and the
splitter-hub/cabinet (15,300 m). No signal is detectable beyond the fault point. Immediate dispatch of a
field crew is required to locate and repair the cable at the 5.0 km mark.
2. Link Identification and Configuration
2.1 Port Configuration
| ALM Device | ADVA FSP3000 ALM Simulator — S/N: SIM0001 |
| Firmware Version | 6.6.1 |
| Software Build | 60501_202405141302 |
| Port Number | MCH-1-3 (Port 3) |
| Port Name | FTTH feeder — mixed build |
| Administrative State | In-Service |
| Monitoring Mode | Fingerprint (continuous monitoring enabled) |
2.2 Fiber Specification
| Fiber Type | ITU-T G.652.D (Corning SMF-28e+) |
| Refractive Index (IOR) | 1.4682 @ 1550 nm |
| Core / Cladding | 9 / 125 µm |
| Operating Wavelength | 1550 nm |
| Nominal Link Length | 19,600 m (19.6 km) |
| Fiber Attenuation Coefficient | ~0.20 dB/km @ 1550 nm (typical G.652.D) |
2.3 Link Budget Configuration
| Link Budget Margin | 5.0 dB |
| Link Budget Warning Margin | 3.0 dB |
| Loss Budget Margin | 2.0 dB |
| Loss Budget Warning Margin | 1.5 dB |
| Maximum Laser Power | 12.0 dBm |
| Coupler Loss | 0.70 dB |
3. Alarm Event Details
3.1 Alarm Information
| Alarm Type | LINK LOSS HIGH |
| Severity | CRITICAL (Severity 2) |
| Detection Timestamp | 2026-02-15 18:49:31 UTC+8 |
| Measured Link Loss | 100.00 dB (sentinel: complete signal loss) |
| Fault Loss | 93.86 dB |
| Coupler Loss | 0.70 dB |
| Alarm Status | ACTIVE (not cleared) |
3.2 Event Timeline
2026-02-15 18:49:31
CRITICAL
Link Loss High alarm SET on Port 3 — measured loss 100.00 dB
2026-02-15 18:49:33
SYSTEM
Automatic Fault Analysis started on Port 3
2026-02-15 18:49:36
SYSTEM
Automatic Fault Analysis completed — saved as Measurement ID 143
2026-02-15 18:50:23
INFO
OTDR Measurement started (admin-initiated)
2026-02-15 18:50:26
INFO
OTDR Measurement completed — saved as Measurement ID 144
2026-02-15 18:50:39
INFO
Manual Fault Analysis started (admin-initiated)
2026-02-15 18:50:42
INFO
Manual Fault Analysis completed — saved as Measurement ID 145
2026-02-16 04:35:xx
INVESTIGATION
Confirmation OTDR shot executed — Measurement ID 146 — failure confirmed
2026-02-16 04:36:xx
INVESTIGATION
Full failure OTDR measurement executed — Measurement ID 147 — fiber break verified
2026-02-16 04:37:xx
INVESTIGATION
Comparative Fault Analysis executed — Measurement ID 148 — break at 5,000 m confirmed
4. Baseline Reference Data
4.1 Historical Performance
| Measurement |
ID |
Date |
Total Loss |
Link Length |
Status |
| Fingerprint (Reference) |
118 |
2026-02-15 17:21:08 |
~6.14 dB |
19,600 m |
PASSED |
4.2 Baseline Event Table
| Event # |
Distance (m) |
Type |
Loss (dB) |
Reflectance (dB) |
Description |
| 1 |
150 |
Connector |
0.20 |
-45.0 |
ODF / patch-panel connector |
| 2 |
15,300 |
Splice / Splitter |
0.40 |
-60.0 |
Splitter-hub / street cabinet |
| 3 |
19,600 |
End of Fiber |
— |
-5.0 |
End reflection (reflective termination) |
4.3 Normal Operating Parameters
| Baseline Link Loss | ~6.14 dB |
| Fiber Attenuation (19.6 km x 0.20 dB/km) | ~3.92 dB |
| Number of Connectors | 1 (ODF at 150 m) |
| Number of Splices / Passive Elements | 1 (splitter-hub at 15,300 m) |
| Connector Loss (total) | 0.20 dB |
| Splice / Splitter Loss (total) | 0.40 dB |
| Excess Loss (other) | ~1.62 dB |
| Available Link Budget Margin | > 5.0 dB |
5. OTDR Measurement Protocol
5.1 Confirmation Shot (Initial Verification)
Purpose: Rapid verification of alarm condition before committing to full measurement cycle.
| Measurement ID | 146 |
| Timestamp | 2026-02-16 ~04:35 UTC |
| Wavelength | 1550 nm |
| Pulse Width | 200 ns |
| Range | 24,000 m (24 km) |
| Averaging Time | 30 seconds |
| Refractive Index | 1.4682 |
| Result | FAILURE CONFIRMED — complete signal loss beyond 5,000 m |
5.2 Full Failure Measurement (Detailed Analysis)
| Parameter |
Value |
Standard Reference |
| Measurement ID |
147 |
— |
| Timestamp |
2026-02-16 ~04:36 UTC |
— |
| Wavelength |
1550 nm |
ITU-T G.650.1 |
| Pulse Width |
200 ns |
TIA-455-8-B |
| Range |
24,000 m (24 km) |
— |
| Averaging Time |
180 seconds (high accuracy) |
— |
| Index of Refraction |
1.4682 |
ITU-T G.652 |
| Spatial Resolution |
~20 m (200 ns pulse) |
TIA-455-8-B |
| Measurement Uncertainty |
±1.0% distance, ±0.05 dB loss |
ISO/IEC Guide 98-3 |
| Result |
Fiber break confirmed at ~5,000 m |
— |
5.3 Fault Analysis (Comparative)
| Measurement ID | 148 |
| Reference Baseline | Fingerprint ID 118 (2026-02-15 17:21:08) |
| Fault Position | 5,000 m (5.0 km) |
| Fault Loss | 93.86 dB |
| Total Link Loss | 100.00 dB |
| Signal Beyond Fault | NONE (noise floor only) |
6. OTDR Trace Analysis
6.1 Baseline vs. Current — OTDR Comparison Diagram
Figure 1: OTDR Trace Comparison — Baseline Fingerprint (green) vs Current Fault Analysis (red) — Port MCH-1-3
Professional ALM-style diagram showing the baseline fingerprint (green trace, healthy link state from 2026-02-15)
overlaid with the current fault analysis measurement (red trace). The baseline shows the complete 19.6 km link with
all events (ODF connector at 150 m, splitter-hub at 15,300 m, and end-of-fiber reflection at 19,600 m). The current
trace shows an abrupt signal termination at approximately 5.0 km, characteristic of a complete fiber break. No signal
is detectable beyond the break point. Numbered event markers and shaded uncertainty regions annotate the failure location.
6.2 Trace Interpretation
The overlay comparison clearly reveals the catastrophic nature of this failure. The green baseline trace follows the
expected profile of the 19.6 km FTTH feeder link: a gradual linear attenuation of approximately 0.20 dB/km, punctuated
by discrete events at the ODF connector (150 m) and the splitter-hub (15,300 m), terminating with a strong end-of-fiber
reflection at 19,600 m.
The red current trace tracks the baseline identically for the first ~5.0 km, confirming that the fiber section from the
ALM port to the break point remains intact and undamaged. At 5.0 km, the trace drops abruptly to the noise floor with a
measured fault loss of 93.86 dB. This signature — sudden signal termination with no recoverable backscatter beyond
the event — is the definitive OTDR signature of a complete fiber break.
The ODF/patch-panel connector at 150 m shows identical characteristics in both traces (loss 0.20 dB, reflectance -45.0 dB),
confirming that all equipment at the headend is functioning normally. The splitter-hub at 15,300 m and end-of-fiber at
19,600 m are both beyond the break point and therefore not visible in the current measurement.
7. Failure Analysis
7.1 Link Loss Budget Analysis
| Component |
Baseline (dB) |
Current (dB) |
Delta (dB) |
Status |
| Total Link Loss |
~6.14 |
100.00 |
+93.86 |
EXCEEDED |
| Fiber Attenuation (0-5 km) |
~1.00 |
~1.00 |
0.00 |
NORMAL |
| ODF Connector (150 m) |
0.20 |
0.20 |
0.00 |
NORMAL |
| Splitter-hub (15,300 m) |
0.40 |
N/A (beyond break) |
— |
NOT REACHABLE |
| Fault Event at 5,000 m |
— |
93.86 |
+93.86 |
FIBER BREAK |
| Available Margin |
> 5.0 dB |
0.00 dB |
— |
ZERO MARGIN |
7.2 Failure Localization
| Failure Distance | 5,000 m (5.0 km from ALM port) |
| Localization Uncertainty | ±50 m (based on 200 ns pulse width) |
| Failure Range | 4,950 m to 5,050 m |
| Nearest Known Event (upstream) | ODF connector at 150 m (4,850 m before break) |
| Nearest Known Event (downstream) | Splitter-hub at 15,300 m (10,300 m after break) |
| Route Section | Feeder cable between ODF and splitter-hub |
| GPS Coordinates | N/A — requires GIS correlation with cable route map |
Localization Method: Two-way transit time calculation per ITU-T G.650.1.
Distance = (Time × c × n) / 2, where c = 2.998 × 108 m/s, n = 1.4682.
Uncertainty based on pulse width and sampling resolution.
7.3 Failure Classification
| Failure Type | FIBER BREAK (Complete Fracture) |
| Event Loss | 93.86 dB |
| Reflectance at Break | High (> -40 dB) — consistent with cleaved/fractured glass face |
| Signal Beyond Event | NONE — noise floor only, no backscatter detectable |
| Backscatter Change | Abrupt termination from ~-30 dB baseline to noise floor |
| Event Width | < 20 m (sharp, non-distributed) |
7.4 Root Cause Assessment
The OTDR signature is unambiguous: a complete fiber break characterized by (1) abrupt total signal loss at
a single discrete point, (2) high reflectance indicating a glass-air interface at the fracture, and
(3) zero detectable signal beyond the event. The event is not consistent with macrobending (which would show
gradual loss increase and possible recovery), connector degradation (which would appear at a known event location),
or splice failure (which would show increased loss but not total termination).
The break location at 5.0 km falls in the feeder cable section between the ODF (150 m) and the splitter-hub
(15,300 m). This section typically runs through outdoor plant infrastructure (ducts, aerial cable, or direct-buried).
Common causes for breaks in this section include:
- Third-party dig-up / construction damage (most common cause of feeder breaks)
- Vehicle impact on aerial cable or pedestal
- Storm damage, falling trees, or ice loading
- Rodent damage in direct-buried sections
- Duct collapse or conduit failure
Confidence Level: HIGH (95%). The OTDR signature is definitive for a fiber break. Field verification
is required to determine the specific physical cause.
7.5 Fault Analysis Event Comparison
| Event # |
Distance (m) |
Reflectance (dB) |
Loss (dB) |
Baseline Match |
Notes |
| FA-1 |
150 |
-45.0 |
0.20 |
Matches baseline |
ODF connector — operating normally |
| FA-2 |
15,300 |
-60.0 |
0.40 |
Beyond break |
Splitter-hub — not reachable, ghost from baseline |
| FA-3 |
19,600 |
-5.0 |
— |
Beyond break |
End of fiber — not reachable, ghost from baseline |
8. Resolution Status
8.1 Current Link State
| Parameter |
Value |
Threshold |
Status |
| Total Link Loss |
100.00 dB |
Link budget + 5.0 dB margin |
EXCEEDED |
| Available Margin |
0.00 dB |
> 2.0 dB |
ZERO |
| Alarm Status |
ACTIVE (Link Loss High) |
— |
SET |
| Link Operational |
NO |
— |
DOWN |
| Time Since Alarm |
~17 hours 48 minutes |
— |
— |
8.2 Self-Healing Analysis
| Self-Healing Detected | NO |
| Assessment | The failure is a permanent physical break. The OTDR signature shows
a clean fracture with no partial recovery. Self-healing is not possible for this failure type.
Physical repair (fusion splicing or cable replacement) is mandatory. |
9. Recommendations and Action Items
IMMEDIATE ACTIONS (0-4 hours) — Priority: CRITICAL
-
Dispatch Field Crew
Target location: 5.0 km (±50 m) from ALM port along FTTH feeder route.
GPS: Correlate with GIS cable route map to determine street-level address.
Access notes: Verify if section is aerial, ducted, or direct-buried at 5 km mark.
Estimated repair time: 4-8 hours (emergency fusion splice or cable replacement).
-
On-Site Investigation
Check for construction activity, dig-ups, vehicle damage, storm damage, or other physical disturbance
at the 5 km mark. Photograph damage for incident documentation.
-
Traffic / Service Impact
Identify all customers served by this FTTH feeder and initiate customer notification procedures.
Assess if traffic rerouting via protection paths is available.
-
Field Equipment Required
Portable OTDR for on-site verification, fusion splicer, fiber cleaver, splice enclosure,
replacement cable stock (if needed), OTDR launch cable.
FOLLOW-UP ACTIONS (24-72 hours)
-
Post-Repair Verification
Execute bidirectional OTDR measurement after repair to verify splice quality (< 0.10 dB loss target)
and confirm full link continuity to 19,600 m end-of-fiber.
-
Link Budget Verification
Verify total link loss is within budget margins. The repair splice will add ~0.05-0.10 dB to
the total path loss. Confirm margin > 2.0 dB.
-
Update Baseline Fingerprint
After successful repair, execute a new fingerprint measurement to establish the post-repair baseline.
The repaired link will have one additional splice event at ~5.0 km.
-
Documentation
Update cable plant records with new splice location. File damage report if third-party caused.
Update GIS system with repair coordinates.
9.3 Preventive Maintenance
- Review cable route protection at 5 km mark — consider duct reinforcement or protective conduit if currently direct-buried
- Verify "Call Before You Dig" (CBYD) markings are current and accurate for this section
- Consider installing cable warning markers/tape if not already present
- Monitor the repaired link at increased frequency (every 15 minutes) for 48 hours post-repair
- Schedule routine OTDR survey of the full feeder route within 30 days
10. Technical Appendices
10.1 Complete Event Table
| Event # |
Distance (m) |
Type |
Loss (dB) |
Reflectance (dB) |
Comments |
| 0 |
0 |
Port / Launch |
0.00 |
— |
ALM Port MCH-1-3 output |
| 1 |
150 |
Connector |
0.20 |
-45.0 |
ODF / patch-panel — normal (matches baseline) |
| 2 |
5,000 |
FIBER BREAK |
93.86 |
> -40.0 |
PRIMARY FAULT — complete fiber fracture |
| 3 |
15,300 |
Splice / Splitter |
0.40 |
-60.0 |
Beyond break — from baseline reference only |
| 4 |
19,600 |
End of Fiber |
— |
-5.0 |
Beyond break — from baseline reference only |
10.2 Measurement Quality Metrics
| Signal-to-Noise Ratio | > 3 dB (sufficient) — PASS |
| End-of-Fiber Detection | NOT DETECTED (fiber broken before end) |
| Trace Saturation | NONE — PASS |
| Measurement Completion | 100% (no errors) — PASS |
| Baseline Correlation (0-5 km) | Excellent — traces match within 0.05 dB |
| Dead Zone After Launch | ~50 m (within specification for 200 ns pulse) |
10.3 Measurement History Summary
| ID |
Type |
Timestamp |
Purpose |
Result |
| 118 |
Fingerprint |
2026-02-15 17:21:08 |
Baseline reference |
HEALTHY |
| 143 |
Auto Fault Analysis |
2026-02-15 18:49:36 |
Automatic response to alarm |
BREAK @ 5 km |
| 144 |
OTDR |
2026-02-15 18:50:26 |
Admin-initiated measurement |
BREAK @ 5 km |
| 145 |
Fault Analysis |
2026-02-15 18:50:42 |
Admin-initiated fault analysis |
BREAK @ 5 km |
| 146 |
OTDR (Confirmation) |
2026-02-16 ~04:35 |
Investigation confirmation shot |
BREAK @ 5 km |
| 147 |
OTDR (Full) |
2026-02-16 ~04:36 |
High-accuracy failure measurement |
BREAK @ 5 km |
| 148 |
Fault Analysis |
2026-02-16 ~04:37 |
Comparative analysis vs baseline |
BREAK @ 5 km |
11. Report Metadata
| Report ID | FLR-MCH-1-3-20260216-00001 |
| Generated By | Fiber Engineer AI Agent v1.0 |
| Analysis Engine | Claude Opus 4.6 (Anthropic) |
| Report Generation Time | 2026-02-16 12:37:00 UTC+8 |
| Investigation Duration | ~8 hours (alarm at 18:49 to report at 12:37 next day) |
| ALM Device Serial | SIM0001 |
| Firmware Version | 6.6.1 |
| Software Build | 60501_202405141302 |
11.1 Standards and References
| Standard |
Title |
| ITU-T G.650.1 |
Definitions and test methods for linear, deterministic attributes of single-mode fibre and cable |
| ITU-T G.652 |
Characteristics of a single-mode optical fibre and cable |
| ITU-T L.40 |
Optical fibre outside plant maintenance support, monitoring and testing system |
| ITU-T L.41 |
Maintenance wavelength on fibres carrying signals |
| TIA-455-8-B |
Measurement of fiber point discontinuities using an OTDR |
| TIA/EIA-526-7 |
Optical power loss measurements of installed single-mode fiber cable plant |
| IEC 61280-4-1 |
Fibre-optic communication subsystem test procedures — Cable plants and links |
| ISO/IEC Guide 98-3 |
Uncertainty of measurement — Guide to the expression of uncertainty in measurement (GUM) |
12. Approval and Distribution
| Role |
Name |
Signature |
Date |
| Generated By |
Fiber Engineer AI Agent v1.0 |
[Auto-generated] |
2026-02-16 |
| Reviewed By |
[NOC Engineer] |
|
|
| Approved By |
[Network Manager] |
|
|
Distribution List
- Network Operations Center (NOC) — Immediate
- Field Operations / Outside Plant Team — Immediate (with dispatch order)
- Customer Service — For customer notification (FTTH feeder serves end-users)
- Network Planning — For route review and preventive measures
- Management — For awareness (critical service-affecting event)
Disclaimer
This report was automatically generated by the Fiber Engineer AI Agent in accordance with industry best
practices and international standards for fiber optic testing and analysis (ITU-T L.40, TIA-455-8-B).
All measurements and analyses follow ITU-T and TIA/EIA methodologies. Field verification is required
to confirm the root cause and exact location of the failure. Measurement uncertainties are stated
where applicable per ISO/IEC Guide 98-3.
Report ID: FLR-MCH-1-3-20260216-00001
Classification: Internal — Network Operations
Retention: 7 years per ITU-T L.40 recommendations