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40G QSFP Transceivers for QSFP 4x10G Breakout Connectivity Guide

Author Patrick

Date 10/23/2021

40G QSFP+ optical transceiver is a solution to increase bandwidth from 10G to 40G connection. 4x10G QSFP optical module provides low power consumption, high density, and cost-effectiveness for data centers migrating to 40 Gigabit Ethernet This article will make you have a better understanding of QSFP 4x10G modules by introducing the working principle, transceiver types, and connection cable solution of 40G to 4x10G breakout cable for you.

What is QSFP 4x10G Transceiver and How Does It Work?


The 40G QSFP (Quad Small Form-factor Pluggable) optical module is designed specifically for high density, high speed, and hot-pluggable applications. It is structured by 4 individual transmit channels and 4 individual receiver channels, each of which enables 10Gbps. The 4 channels can also be combined into a total of 40 Gigabit Ethernet links. 


The working process of the 4x10G QSFP+ transceiver is: In the transmit direction, four-channel of 10Gbit/s electric signals are transmitted over the electric interface to the 4-channel VCSEL laser. The electric signals convert to optical signals through the VCSEL laser. Reversely, in the receive direction, the optical signals convert to high-speed electric signals through 4-channel PIN. Fig. 1 shows the working principle of the 4x10G QSFP+ transceiver.


QSFP 40G transceiver working principle

Fig.1 – 4x10G QSFP transceiver working principle



Which 40G QSFP+ Transceivers Can be Used in 4x10G Connectivity?


1. QSFP 40G SR4 and QSFP 40G CSR4 MTP/MPO Transceiver for 4x10G mode


QSFP 40G SR4 optical module enables high-bandwidth 40G optical links over 12-fiber MPO/MTP female connectors at the wavelength of 850nm and supports link lengths of 100m on OM3 and 150m on OM4. It also can be used in a 4x10G breakout mode for interoperability with 10GBASE SR modules. The 4x10G connectivity is achieved using a 12-fiber MTP/MPO parallel to a 2-fiber duplex LC multimode breakout cable, which connects the QSFP SR4 optical transceiver to four SFP+ SR optical modules. Fig. 2 shows how to achieve QSFP-40G-SR4 to 4xSFP-10G-SR connection and required 40G to 4x10G breakout MMF cable.

Similarly, 40G QSFP+ CSR4 optical module also can be used in a 4x10G breakout connectivity with MTP/MPO parallel to duplex LC fiber breakout cables for connectivity to four 10GBASE-SR interfaces. The difference is 40Gb QSFP+ CSR4 extends the length link up to 400m over OM4 multimode cable. 

QSFP 40G SR4 to 4x10G SFP+ SR connection with MTP female to 4 LC Duplex multimode breakout cable


Fig.2 – QSFP 40G SR4 to 4x10G SFP+ SR connection with MTP female to 4 LC Duplex multimode breakout cable


2. QSFP 40G LR MTP/MPO Transceiver for 4x10G mode


QSFP 40G LR optical transceiver supports 10km transmission distance over Single-mode Fiber (SMF), which enables 40G data rates over 12-fiber parallel fiber with MPO/MTP multifiber connectors. 40G QSFP LR transceiver can also be used in a 4x10G connectivity to fulfill interoperability with 10G SFP+ LR transceivers. The 4x10G connectivity is achieved by using a 12-fiber MTP Female to a 2-fiber single-mode duplex breakout cable, which connects the QSFP 40G LR module to four 10GBASE-LR optical ports. Fig. 3 shows how to achieve QSFP 40G LR to 4x10G SFP+ LR connection and the required 40G to 4x10G SMF breakout cable.


QSFP 40G LR to 40x10G SFP+ LR connection with MTP female to 4 LC duplex single-mode breakout cable


Fig.3 – QSFP 40G LR to 40x10G SFP+ LR connection with MTP female to 4 LC duplex single-mode breakout cable



3. Do QSFP 40G LR4 LC and QSFP 40G ER4 LC support 4x10G connectivity?


The answer is no. The reason you will know by learning the working process illustrated next of 40G QSFP+ LR transceivers. QSFP 40G LR4 module adopts CWDM (Coarse Wavelength Division Multiplexing) technology. It supports the link up to 10km over a pair of SMF with duplex LC connectors. In the transmit direction, 4x10Gbe serial digital signal transmit to DML laser with four wavelengths of 1271nm, 1291nm, 1311nm, and 1331nm. Then 4 CWDM optical signals are multiplexed to a single-mode fiber over an LC connector. In the receive direction, 40G CWDM optical signals input and demultiplex into 4 individual 10G optical data streams with different wavelengths, as shown in Fig. 4. QSFP ER4 works similarly to QSFP LR4. Fig. 4 shows the working principle of the QSFP+ LR4 transceiver. By learning the working process of QSFP-40G-LR4 and QSFP-40G-ER4, understandably, they can't be split into 4 individual duplex SMF fiber to achieve 4x10G connectivity with duplex LC connector structure.


QSFP+ LR4 and ER4 transceivers working principle 

Fig.4 – QSFP+ LR4 and ER4 transceivers working principle





From the above discussion, we learn the working principle of QSFP 4x10G transceivers and 4x10G connectivity supported 40G QSFP+ transceivers types are QSFP-40G-SR4, QSFP-40G-CSR4, QSFP-40G-LR, which are structured with MTP/MPO connectors in common. As a low power consumption, high density, and cost-effective solution for 10G to 40G migration, QSFP 4x10G transceivers have been widely applied in data center interconnection, especially for short-distance high-speed transmission.

QSFPTEK has been focusing on the R&D and production of high-speed optical interconnect products for 10 years. QSFP 4x10G transceivers and supported MTP/MPO to LC breakout cables are available at the best price. Contact us and get a quote.



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