QSFP+ 40G TRANSCEIVERS
From the UK’s High Data Rate Connectivity Specialists
40G OVER MULTIMODE FIBRE
Short range parallel (SR4) transmission
40G over Singlemode Fibre
Long range serial and parallel transmission
40G parallel transmission over multimode fibre
QSFP+ transceivers are hot-pluggable 40G Ethernet Quad Small Form-Factor modules that transmit over multimode (OM3 or OM4) fibre @850nm using 40GBASE-SR4. These are now widely used across short to mid-range data centre applications within the core and aggregation layers or within spine switch connection, connection to routers or storage area networks (SAN).
Transmission
40GBASE-SR4 transceivers transmit four 10G (SR equivalent) channels using 8 fibre cores (4 duplex pairs) to give an aggregate bandwidth of 40Gbps. To achieve the 8 fibre connections the QSFP+ has a single MPO (Multi-fibre Push On) port and requires a similar 8 fibre connector cable (typically with an MTP type MPO connector).
There is an added benefit of using 4 duplex pairs to transmit the 40G signal in that each 10G lane can be connected to a different switch enabling one 40G port to connect to up to 4 other 10G ports.
An alternative to SR4 transmission over eight fibres (parallel transmission) is using just two fibres (SR protocol) via a transceiver such as a Cisco bi-directional (BiDi) transceiver. These transceivers transmit 2 x 20G lanes to give 40G but do so at two wavelengths to enable transmission over the same fibre (in a similar way to singlemode 40G transmission). The benefit is that the signal can use existing 10G infrastructure. The downside is that the 40G cannot be split to 4 x 10G ports.
Distance
When following recognised cabling standards, QSFP+ SR4 transceivers can transmit 40 Gbps Ethernet up to 100 meters over OM3 multimode fibre or up to 150 meters using OM4 multimode fibre cable. In reality, the actual transmission distances is greater than this due to the “slack” built into the standards and the improvement in transceiver technology since the standards were ratified.
Type | Distance | Transmitter | Power | Standard |
40G SR4 | 100m OM3 and 150m OM4 | VCSEL | 1.5 (max) | IEEE 802.3ba |
40G eSR4 | 300m OM3 and 400m OM4 | VCSEL | 1.5 (max) | IEEE 802.3ba |
40G OVER SINGLEMODE FIBRE
Whereas there is only one type of transceiver for 40G over multimode fibre, an SR4 transceiver, there are several types of singlemode transceiver and two methods of transmission.
Serial Transmission Transceiver
These transceivers are capable of transmitting 40G over two fibres. Four separate wavelengths are simultaneously transmitted to carry four 10G lanes of data. These transceivers have an LC duplex port and depending on the type can have a maximum transmission distance from 2 km to 40km.
Type | Distance | Transmitter | Power | Standards |
40G IR4 | 2 km | VCSEL | 3.5V (max) | IEEE 802.3ba |
40G LR4 | 10 km | 4 x 10 Gbps CWDM | 3.5V (max) | IEEE 802.3ba |
Parallel Transmission
A QSFP+ PIR4 and PLR4 transceiver transmits 40G over 8 fibres with each of the four independent lanes 10G using two fibres. To do this the transceiver has an MPO port and requires connection to MPO patch cables.
One of the main benefits of these transceivers is that the 40G port can easily be connected to four 10G ports using a fibre breakout cable.
Type | Distance | Transmitter | Power | Standards |
40G PIR4 | 2 km | VCSEL | 3.5 (max) | Compliant IEEE 802.3ba |
40G PLR4 | 10 km | 4 x 10 Gbps over 4 wavelengths | 3.5 (max) | Compliant IEEE 802.3ba |