The project deployed the Olycom OM5800 platform with the following architecture:
Client Side → OTU (T4Q2) → MUX/DEMUX (OMD08) → EDFA (BA+PA) → Band Splitter → Single Fibre → Band Splitter → EDFA (PA+BA) → MUX/DEMUX → OTU → Client Side
The key to enabling single-fibre coherent transmission is the Band Splitter, which divides the C-band into two separate wavelength bands:
- Red band (1545–1565nm) — carries traffic from Site 1 to Site 2
- Blue band (1530–1545nm) — carries traffic from Site 2 to Site 1
The 400G coherent CFP2 module itself is a BiDi transceiver — it uses a single optical port, with Tx on the red band and Rx on the blue band.
This eliminates the backscatter issue at the transceiver level, while the Band Splitter provides passive wavelength isolation at the line side.
No special fibre or active components are required to achieve bidirectional separation.
Why Single-Fibre DWDM?
Q: Why choose single-fibre over a conventional dual-fibre deployment?
Single-fibre DWDM cuts fibre infrastructure requirements in half, directly reducing both leased fibre costs and civil works expenditure.
For long-haul routes where fibre availability is limited or expensive, this represents a significant operational and capital saving.
The Band Splitter is a fully passive component with no power requirement, adding negligible complexity while enabling the single-fibre architecture.
Combined with coherent BiDi transceivers, the solution delivers 400G capacity with the same fibre footprint as a traditional single-channel system.
Key Deployment Parameters
Span Distance: 90km
Span Loss: ~25dB
Line Side Capacity: 400G (4×100G aggregated)
Transceiver Type: 400G Coherent CFP2 BiDi
Client Interfaces: 4×100G QSFP28 (100GBASE-LR4)
Amplification: OBA20/G12 (Booster) + OPA16/G20 (Pre-amp) per direction
Mux/Demux: OMD08 — 8-channel C21–C28 100GHz DWDM
Single-Fibre Technology: Band Splitter (C-band red/blue separation)
Management: OM5800 NMS via Web GUI and SNMP
Application Expansion: Beyond Point-to-Point Links
While this deployment focused on a point-to-point long-haul link, the same OM5800 platform and single-fibre BiDi approach is applicable across a range of network scenarios.
1. Metro and Regional Networks
City-to-city or data centre interconnect links where fibre is at a premium benefit directly from single-fibre DWDM, doubling effective capacity on existing infrastructure.
2. Enterprise and Campus Networks
Organisations with limited dark fibre between campuses or buildings can use single-fibre DWDM to maximise bandwidth without additional fibre deployment.
3. Mobile Backhaul and 5G Fronthaul
As 5G networks scale, fronthaul and backhaul links increasingly require high-capacity, low-latency transport. Single-fibre coherent DWDM provides an efficient upgrade path without major fibre infrastructure changes.
Frequently Asked Questions
Q: How does the Band Splitter solve the backscatter problem?
The Band Splitter assigns each transmission direction to a different portion of the C-band — red (1545–1565nm) and blue (1530–1545nm). Because the BiDi CFP2 transceiver transmits and receives on different wavelength bands, its own backscattered light falls outside the receive band and is filtered out, preventing interference.
Q: Is the Band Splitter an active component?
No. The Band Splitter is fully passive — it requires no power and introduces no active failure points. This contributes to the overall reliability of the single-fibre solution.
Q: Can the OM5800 platform be managed remotely?
Yes. The OM5800 NMS provides a web-based GUI for real-time monitoring of all transceiver parameters including Tx/Rx power per channel, alarm thresholds, temperature, voltage, and LOS state. SNMP polling integration is also supported for automated network management systems.
Q: What client interfaces are supported?
The T4Q2 OTU card supports 4×100G QSFP28 client interfaces, aggregating into a single 400G coherent CFP2 line side signal. The platform also supports higher capacity configurations for future network growth.
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