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With the rise of the Internet and various network services in recent years. The capacity demand for routers (especially core routers) has been increasing. In the actual operating network, the capacity demand of individual core nodes has reached the Tbit/s level. It is foreseeable that core routers will usher in the era of 40G ports. With the rise of 40G Ethernet, a large number of QSFP+ optical modules of various types have been developed. Such as the 40GBASE-SR4, and in this article, we will introduce some details of the development of 40G optical modules and introduce the 40GBASE-SR4.
What is a 40GBASE-SR4 Transceiver?
The 40GBASE-SR4 can installed and accessed very easily. It designed to be plug-and-play and also supports hot-swapping. Widely used in fiber optic switches, routers, NICs, servers, or other fiber optic devices with 40Gb QSFP+ ports. QSFP+ 40G SR4is typically used with OM3 or OM4 MMFs, with a maximum transmission distance of 100m on OM3 and 150m on OM4. The transmit wavelength of 40GBASE-SR4 is 850nm. This transceiver is fully compliant with QSFP+ MSA (SFF-8436) and IEEE 802.3ba 40GBASE-SR4 protocols.
The 40GBASE-SR4 reduces the cost, complexity, and number of spare parts for OAM. Especially in metro backbone networks, and provides better scheduling and integration than four 10G systems to reduce equipment stacking and room footprint. The use of QSFP+ 40G SR4 optical modules also offers greater cost savings than other solutions. 40GBASE-SR4 and 10GBASE-SR4 both operate at 850nm, which also allows for multiple data links to enhance the core network functionality.
What Technologies Used in 40GBASE-SR4?
Optical Signal-to-Noise Ratio Improvement Technology
Compared with 10Gbit/s WDM system, 40Gbit/s WDM system has more optical signal-to-noise ratio (OSNR, dispersion, non-linear effect, PMD, and a series of other problems, for 40Gbit/s system, the OSN of the system needs to improve by 6~8 dB to achieve the same transmission BER as 10Gbit/s system).
Dispersion CompensationTechnology
Theoretically, both chromatic dispersion cost and polarization mode dispersion cost grow with the square of the bit rate. So the dispersion and PMD tolerance of 40G is 16 times lower than that of 10G, which is very difficult to achieve. Since the dispersion tolerance of less than 100ps/nm is very small. It may cause extremely serious limitations for the 40Gbit/s system. So from the perspective of system design flexibility and economy. The variable dispersion compensator (VDC) should be used for automatic compensation.
It is caused by the asymmetry of the fiber core and by internal and external stresses (e.g., bending of the fiber). Due to the introduction of birefringence, the two propagating polarization modes in the fiber undergo differential group delay (DGD). Which leads to pulse broadening, i.e., inter-code interference (ISI) and an increase in the bit error rate.
Conclusion
This article introduces the technology used in the development of 40G optical modules and introduces the 40GBASE-SR4 modules. I believe you have a better understanding of these. 40GBASE-SR4 is generally used to build 4x10G optical links. That used to build high-density transmission, or used in 40G to 40G connections.
The QSFP+ 40G SR4 module has been widely used in the market because of the cost savings to data centers. If you would like to learn more about the 40GBASE-SR4, you can contact QSFPTEK customer service via sales@qsfptek.com. QSFPTEK is a third-party manufacturer of high-quality, cost-effective optical modules including the 40GBASE-SR4 and a range of other related products.