Which SFP transceiver and fibre type to use for White Rabbit
Standard compatible to 1000BASE-BX10
As in White Rabbit it is of uttermost importance to have equal cable lenghts in both directions, a single fibre should be used for sending data both directions.
As we claim a compatibility with Ethernet, we use what the Gigabit Ethernet standards propose:
http://en.wikipedia.org/wikis/Gigabit_Ethernet: "1000BASE-BX10 is a
capable of up to 10 km over a single strand of single-mode fiber, with a
different wavelength going in each direction.
The terminals on each side of the fibre are not equal, as the one
transmitting "downstream" (from the center of the network to the
outside) uses the 1490 nm wavelength, and the one transmitting
"upstream" uses the 1310 nm wavelength."
With 'terminals' is meant terminal at a high level, not the connectors. The norm is IEEE Std 802.3-2008 (section 59, pdf page 95), but it's not clear from the specification what connectors (LC or SC) they propose for the two sides. Searching for "1000BASE-BX10 connector" comes up with LC connectors (mostly for Cisco).
Conclusion: White Rabbit should follow the 1000BASE-BX10 standard and
use 1310/1490 pairs with a single LC connector.
More specifically, the Switch ports transmitting downstream (to
endpoints) should use 1490nm on the transmitter and 1310nm on the
receiver.
| Transmitting Downstream | Transmitting Upstream | |
|---|---|---|
| Usual location | Switch (e.g., port 3-18) | End node (e.g., SPEC, SVEC) |
| White Rabbit | Master | Slave |
| ITU-T terminology | OLT | ONU |
| Ethernet type | IEEE 802.3ah 1000BASE-BX10-D | IEEE 802.3ah 1000BASE-BX10-U |
| Tx wavelength | 1490 nm | 1310 nm |
| Rx wavelength | 1310 nm | 1490 nm |
Compliant SFP types
| Brand |
Transmitting Downstream Switch (WR Master) |
Transmitting Upstream End node (WR Slave) |
|---|---|---|
| APAC Opto Electronics (with DDMI*) | LS48-C3S-TC-N-B4 - obsolete, replaced by LS48-C3S-TC-N-D4 (green) |
LS38-C3S-TC-N-B9 - obsolete, replaced by LS38-C3S-TC-N-D9 (blue) |
| Axcen Photonics | AXGE-3454-0531 [OLT] (violet) | AXGE-1254-0531 [ONU] (blue) |
| Axcen Photonics (with DDMI*) | AXGD-3454-0531 [OLT] (violet) | AXGD-1254-0531 [ONU] (blue) |
| CBO (with DDMI*) - MTBF report | BO15C4931620D-BO (Version compatible to: BlueOptics Bidi SFP Transceiver 1000BASE-BX-D 20KM) (orange) | BO15C3149620D-BO (Version compatible to: BlueOptics Bidi SFP Transceiver 1000BASE-BX-U 20KM) (blue) |
| Zyxel (with DDMI*) | SFP-BX1490-10 (EOL) | SFP-BX1310-10 (EOL) |
*DDMI: Digital Diagnostics Monitoring Interface reporting Temperature, Transmitted and Received power.
Fibre G652 type
Use G652 fibre. This fibre is optimised for 1310nm, which compensates for the dispersion wavelength of the worst of the two wavelengths used.
- White Rabbit should follow the 1000BASE-BX10 standard and use 1310/1490 pairs with a single LC connector
- Measuring propagation delay over a 1.25 Gbps bidirectional data link - Appendix A (note: images for 1550 instead of 1490, results will be similar)
- The cable type is important that kind of has to be the best at the wavelength of the worst laser.
Other information
- Copper SFP types
- Non-compliant SFP types
- SFP+ I2C Project
- SFP standards at SNIA SFF Working group
Achim Vollhardt, Erik van der Bij, Daniel Florin - 30 March 2020