France National Strategic Backup Fiber: 96 Monitoring Units with 8-Channel Optical Switches Across 8 Sites, Delivered in 3 Months

Snapshot

• Customer: Operator/manager of a France national strategic backup fiber cable (name withheld at customer request)
• Project scale: 8 monitoring sites; 96 fibers per cable; 12 monitoring units per site; 96 units in total
• Core challenge: Real-time visibility into the availability of every fiber to prevent damage; a per-fiber OTDR module design would be too costly and would place excessive load on the lasers; uplink networks at some sites were unstable, so test data could not be uploaded to the control room
• Delivered solution: OTDR + 8-channel optical switch for fiber-by-fiber cycling; one 8-channel optical switch completes cycling of its 8 channels within 1 hour; 12 units per site work in parallel to cover 96 fibers; wired and 4G backup; local caching and retransmission
• Core results: 96 monitoring units installed and commissioned within 3 months; OTDR module count reduced to about one-eighth of a per-fiber OTDR design; data cached locally during uplink outages and retransmitted after recovery
• Capabilities involved: OTDR selection / 8-channel optical switch / cycling strategy / 4G backup / monitoring software / on-site commissioning

Who the Customer Is

The customer is the operator/manager of a France national strategic backup fiber cable, responsible for ensuring that the backup cable remains available when needed. The project covers 8 monitoring sites, with 96 fibers per cable. Because this involves national strategic infrastructure, the customer has high requirements for availability, security, and reliable data backhaul.

Starting Point and Constraints

The customer’s initial idea was to equip every fiber with an OTDR module and test every fiber in real time, so that cable damage or performance degradation could be detected immediately. The direction was correct, but at the scale of 8 monitoring sites and 96 fibers per cable, the problems were straightforward:

• If every fiber were equipped with an OTDR module, the number of OTDR modules and the overall cost would be very high;
• The customer repeatedly emphasized “real time,” but if the OTDR laser were to emit pulses continuously, laser load and service life would be affected;
• Network signals at some monitoring sites were unstable: the equipment could obtain test data but could not reliably upload it to the control room;
• The project required minimizing service interruption and adapting to on-site power and equipment-room conditions.

The customer’s explicit requirements were: monitor the availability of every fiber; locate anomalies to a cable section; ensure stable data backhaul to the control room; control cost; and ensure the equipment adapts to the site environment.

Solution Discussion: Defining “Real Time” and “Cycling” Clearly

We did not quote directly on a “one OTDR module per fiber” basis. Instead, we first held a three-party confirmation with the customer, the operator, and the end user, focusing on three points:

First, replace per-fiber OTDR modules with OTDR + 8-channel optical switches.
Each monitoring unit is equipped with an 8-channel optical switch, which connects 8 fibers one by one to the OTDR test channel in a preset sequence. Each monitoring site uses 12 units, working in parallel to cover 96 fibers. Across 8 sites, the project uses 96 units in total. Compared with a per-fiber OTDR module design, the number of OTDR modules is about one-eighth, significantly reducing overall cost.

Second, “real time” does not mean the laser emits pulses continuously.
What the industry usually calls real-time monitoring is not an OTDR laser emitting continuously 24/7, but completing a cycling cycle within an agreed period. The definition confirmed with the customer for this project was: one 8-channel optical switch completes cycling of its 8 channels within 1 hour; 12 units per site work in parallel to cover the site’s 96 fibers. This detects changes in availability in a timely manner while reducing laser thermal load and extending service life. After confirmation with the operator and end user, the customer agreed to adopt this approach.

Third, add 4G backup for unstable uplink networks.
At some monitoring sites, the wired network was unstable: test data could be obtained but could not be transmitted back to the control room. The solution added 4G transmission modules so that wired and 4G links back each other up. During a network outage, data is cached locally and automatically retransmitted after recovery, avoiding blind spots in the control room.

Specifications and Scope

Process

• Weeks 1–2: Requirements clarification and scale calculation. The customer proposed “one OTDR module per fiber for real-time testing.” We calculated based on 8 sites × 96 fibers: a per-fiber OTDR design would require 768 OTDR modules; with 8-channel optical switches, the project uses 12 units per site and 96 units in total, reducing the OTDR module count to about one-eighth.
• Weeks 3–4: Confirming the definition of “real time.” Through three-party communication with the customer, the operator, and the end user, it was clarified that real-time monitoring would use periodic cycling: one 8-channel optical switch completes cycling of its 8 channels within 1 hour; 12 units per site work in parallel to cover 96 fibers; the laser does not emit continuously. The solution was locked after three-party confirmation.
• Weeks 5–6: Solving data backhaul. In response to unstable networks at some sites, 4G transmission modules were added to back up the wired network; local caching and retransmission mechanisms were added on the device side.
• Weeks 7–10: Delivery and installation. Completed configuration of 96 monitoring units, calibration of 8-channel optical switch channels, OTDR parameter settings, and 4G link testing.
• Weeks 11–12: On-site commissioning and acceptance. At each of the 8 sites, checked the parallel cycling results of 12 units, alarm upload, 4G switching, and retransmission functions; completed training for duty personnel.
• After acceptance: The control room views fiber status based on cycling results; during uplink outages, data is not lost and is retransmitted after recovery.

Results

• 96 monitoring units were installed and commissioned within 3 months, covering 8 monitoring sites with 12 units per site.
• One 8-channel optical switch completes cycling of its 8 channels within 1 hour; 12 units per site work in parallel to cover the site’s 96 fibers.
• By sharing OTDR testing capability through 8-channel optical switches, the OTDR module count is about one-eighth of a per-fiber OTDR design, significantly lowering overall cost compared with a per-fiber module design.
• Avoiding continuous OTDR laser emission reduces laser load and supports long-term stable operation.
• With wired and 4G backup, the problem of test data not being uploadable to the control room at some sites was resolved; data is cached locally during network outages and retransmitted after recovery.
• The customer, the operator, and the end user acknowledged the confirmed solution and delivery progress.

Boundaries and Next Steps

This project does not promise to prevent intentional damage or construction-related excavation damage; it addresses monitoring of fiber availability, cycling tests, and data backhaul only. We do not undertake civil works, equipment-room renovation, or fiber cable emergency repair. The solution is suitable for strategic infrastructure, operators, and private network users that have backup fibers or monitoring fiber resources, need periodic full testing of multi-fiber cables, and face unstable on-site uplink networks.

For next steps, the customer should prepare: fiber allocation tables, a list of monitoring sites, equipment-room power and network conditions, control-room alarm procedures, and confirmation of whether backup fibers may be used for monitoring. For projects involving national strategic facilities, the anonymization scope should be reconfirmed before publishing the case study.

See FirstFiber Technologies OTDRs.