SFP+ 10G BiDi: how to pick the right pair
Need 10G over a single fiber, because only one strand is available between two sites or in your dark fiber? Then you need a BiDi SFP+. Below: how it works, which pair to order, and which reach and coding to pick.
One fiber, two wavelengths
A duplex SFP+ such as 10GBASE-LR uses two fibers. A BiDi SFP+ transmits and receives over a single single-mode fiber, on two different wavelengths. A built-in WDM filter separates the two directions. For 10G BiDi up to 40 km those are 1270 nm and 1330 nm; for 80 km, 1490 nm and 1550 nm.
Always order a pair: U and D
At 20 and 40 km the U variant transmits at 1270 nm and receives at 1330 nm; the D variant transmits at 1330 nm and receives at 1270 nm. In the selector they show as 1270nm TX/1330nm RX and 1330nm TX/1270nm RX. A link only works with one of each: SFP-10G-BX20U-SO goes with SFP-10G-BX20D-SO. So order them together, even if you only manage one end of the link.
Reach: BX20, BX40, BX80
IEEE 802.3cp (2021) standardises 10G BiDi as 10GBASE-BR10, -BR20 and -BR40, for 10, 20 and 40 km. In the market they are often called BX, with the reach in the name. These are the pairs you can order from us:
- 20 km — SFP-10G-BX20U-SO (1270/1330 nm) and SFP-10G-BX20D-SO (1330/1270 nm)
- 40 km — SFP-10G-BX40U-SO (1270/1330 nm) and SFP-10G-BX40D-SO (1330/1270 nm)
- 80 km — SFP-10G-BX80U-SO (1490/1550 nm) and SFP-10G-BX80D-SO (1550/1490 nm)
Always pair a U and D of the same reach, and don't go bigger than you need. A 40 or 80 km optic on a short link can overload the receiver; then you need an attenuator. Check the RX power via DOM after plugging in. The 80 km pair runs on 1490/1550 nm because single-mode fiber has much lower attenuation around 1550 nm than in the O-band around 1310 nm.
Port, connector and fiber
A BiDi SFP+ belongs in an SFP+ port and runs 10G; don't count on it falling back to 1G. For 1G there's the SFP 1G BiDi on 1310/1490 nm. All our BiDi modules have a simplex LC connector; if your fiber comes in on SC, use an SC-LC patch cord. Use single-mode fiber (OS2).
Coding for your platform
Many switches read the vendor ID from the optic's EEPROM and log a warning or keep the port down for a module they don't recognise. So pick your platform under coding: Cisco, Juniper, Arista, MikroTik, Ubiquiti or one of the other vendors in the list. We code the module before it ships. Want a spare pair ready for when an uplink drops? Read how to sort spares and same-day replacement.
