This solution applies 40CH DWDM MUX/DEMUX and some other WDM devices, which can support at most 10x40G links. 40G links will be realised through 4x10G.
And the connection goes like Switch – QSFP+ SR4 – 1×4 MTP-LC harness cable – 10G SFP+ SR – OEO – DWDM 10G SFP+(The following figure would be more clear).
Thus, suppose you use G.625 fibre cable and the cable insertion loss is 0.25dB/km, you can get 3dB system margin in this 80km 40G network.
Equipments for Extending 40G QSFP+ Connection
To extend 40G QSFP+ connection distance, we have to use WDM transponder OEO (Optical-Electrical-Optical) repeater.
OEO repeater allows connection between fibre to fibre Ethernet equipment, serving as fibre mode converter, or as fibre repeater for long distance transmission. It can also function as CWDM/DWDM optical wavelength conversion.
Now we will use a multi-service transport system, including a hot-swappable plug-in OEO card which only occupies 1 slot.
The other space can be left for holding more cards such as DCM, EDFA, OLP. On the left side, there is a card for centralised network management.
This is a 4-channel multi-rate WDM transponder with an OEO-10G card containing 8 SFP/SFP+ slots and can support up to 11.3G rate.
The OEO card can convert 1G~11.3 Gbps Ethernet signals into a corresponding wavelength in CWDM and DWDM network infrastructures. Transmission distance can reach 80 km.
Except WDM transponder OEO repeater, we still need DWDM Mux/Demux and DWDM SFP+ to extend the distance to 80 km.
DWDM Mux/Demux is to combine 4x10G signals of different wavelengths on one single fibre so that it's the best solution to increase network capacity and save cost.
Here we use 40-channel C21-C60 dual fibre DWDM Mux/Demux. So we can choose suitable 10G DWDM SFP+ modules 80km transceiver between the wavelengths of C21 and C60.
For your convenience, the following table introduces the whole equipment to realise 80km 40G connection. About the quantity and transceiver brand, you can select according to your specific needs.
| Equipment | Details |
| Fibre Transceiver | 40GBASE-SR4 QSFP+ 850nm 150m MTP/MPO DOM Transceiver Module |
| 10GBASE-SR SFP+ 850nm 300m DOM Transceiver | |
| C53-C60 DWDM SFP+ 1529.55nm 80km DOM Transceiver | |
| Transponder Repeater | 4 Channels Multi-Rate WDM Converter (Transponder), 8 SFP/SFP+ Slots, Up to 11.3G Rate, Pluggable Module for OTN Platform |
| DWDM Mux/Demux | 40 Channels C21-C60 Dual Fibre DWDM Mux Demux with Monitor Port, 3.0dB Typical IL |
| DWDM EDFA | Customised 1U/2U/4U Managed Chassis Unloaded, Supports up to 8x Multiplexer/EDFA/OEO/OLP Module with Accessories |
| OTN Multiplex Managed Chassis | 20dB Gain Pre-Amplifier DWDM EDFA C-band 13dBm Output, Pluggable Module for OTN Platform |
| Dispersion Compensation Module | 40KM DCF-based Passive Dispersion Compensation Module, 3.5dB Low Loss, LC/UPC, Pluggable Module for OTN Platform |
| MTP-LC Breakout Cable | 8 Fibres MPO to 4 LC Duplex OM4 Multimode Breakout Cable, Type B, 1m |
From this article, you can extend 40Q QSFP+ to 80 km by mainly applying WDM transponder OEO repeater, DWDM Mux/Demux and 10G DWDM SFP+.
