Direct answer
Single-fiber BiDi carries both directions on one strand using matched transmit and receive wavelengths. Verify the paired optic IDs, wavelength ranges, rate and optical interfaces before specifying cords and the route; the BiDi label alone does not establish fiber count.
What single-fiber BiDi means
BiDi means bidirectional transmission. This guide concerns specified single-mode products using one strand and complementary wavelengths; it does not classify every product bearing the BiDi name as a one-strand system.
Cisco's 1G BX10-D and BX10-U example uses a single SMF strand. The D end transmits at 1490 nm and receives at 1310 nm; the U end reverses those wavelengths. An internal WDM splitter separates the light paths. Cisco 1G data sheet
Use this review when single-fiber optics have already been selected for an access or equipment link. Suitability still depends on host support and the complete optical channel.
Official pairing examples
These are nominal wavelengths for the named Cisco products. Check actual transmitter and receiver wavelength ranges before procurement.
| Product pair | First end Tx and Rx | Opposite end Tx and Rx | Optical route |
|---|---|---|---|
| 1G BX10-D and BX10-U | D Tx 1490 nm, Rx 1310 nm | U Tx 1310 nm, Rx 1490 nm | One SMF strand |
| 10G SFP-10G-BXD-I and SFP-10G-BXU-I | D Tx 1330 nm, Rx 1270 nm | U Tx 1270 nm, Rx 1330 nm | One SMF strand |
The second example comes from the 10G SFP+ data sheet. Do not transfer 1G wavelengths to 10G or infer cross-vendor interoperability from U/D suffixes. Cisco 10G data sheet
Cord and route checklist
This table is a proposed procurement record.
| Check | Information to submit | Common omission |
|---|---|---|
| Both optics | Paired part IDs and host support | Only one endpoint specified |
| Wavelength match | Tx and Rx ranges in both directions | A single nominal wavelength |
| Connectors | Interface and polish at every connection | Treating LC shape as a polish definition |
| Fiber route | Working strand, panels and splices | Accidentally using the spare strand |
| Optical conditions | Direction-specific budget and receive-power review | Checking distance only |
| Identification | Device, port, optic direction and strand ID | Losing the pair identity during replacement |
An existing two-strand cable need not automatically be discarded, but the working and spare strands must be identified. Do not silently interpret both paths in a duplex LC assembly as the two directions of the specified single-fiber link.
Acceptance and spares
Keep passive continuity/loss records separate from operating-link validation. Record optic identity and receive status at both ends with the test conditions; a photograph of one illuminated port is insufficient as the complete record.
Manage spares by their approved pairing. A change of vendor requires a fresh peer and host-support review. Acceptance limits come from the selected equipment and project specification.
Procurement FAQ
- Can two U optics form the pair? Use the manufacturer's complementary pair for the specified architecture, not two identical-direction part IDs by assumption.
- Does matching SMF and 10G establish interoperability? No. Check wavelength ranges, peer requirements, host support and optical conditions.
- Does every BiDi product use one strand? No conclusion follows from the name alone. This guide addresses explicitly single-fiber examples.
- Can APC cords be used? Follow the optic documentation. The cited Cisco 1G sheet supports PC/UPC cords and excludes APC; do not generalize to other models.
- What belongs in an RFQ? Paired optic IDs, endpoint interfaces, strand route, length, connection points and acceptance requirements.
Prepare the route record
Provide both optic documents and a port drawing identifying working and spare strands and panel positions. Related pages help review passive-fiber configuration; they do not confirm a particular BiDi supply offering or interoperability.
Related products and technical guides
Sources and review date
Sources checked on 2026-10-10. Manufacturer examples apply only to the cited products. Selection tables and procurement records are editorial recommendations, not ARRANEX performance, certification or supply commitments.
Sources checked: 2026-10-10