High-speed Fibre Optical Transceiver Promoting The Development Of Optical Engine

Mature plug-in package transeivers like 10Gbps XFP transceivers continue to evolve. Transmode in its system integrated XFP-based tunable lasers, called tunable XFP which has important advantages. Opposite to the Menara Networks, integrated the system function to XFP commonly only for line card.

XFP With New Uses

Until now, the deployment of fixed wavelength DWDM XFP means that the system supplier must possess considerable amount of inventory to prepare for operators to deploy new DWDM wavelengths needed.

If there is no inventory, system vendors must order transceivers to the supplier only after waiting for customers to confirm the wavelength, which implies the delivery period of 12-18 weeks. While the use of tunable XFP, just a transceiver can meet the wavelength planning requirements for all operators.

In addition, the optical property of XFP is only slightly after 10 Gbps 300-pin SFF MSA, which only has “2-3dB optical signal-to-noise ratio advantage, means the need for a longer rate to make signal through more optical amplifiers”. Increasing the total achievable rate using the 300 pin packages are available in the 1000km without the use of repeaters.

MSA power and space specifications (such as XFP) are important for component supplier?

It appears important only in a demand. For example, the maximum rated power of XFP is 3.5W, if you use a tunable XFP, a thermoelectric cooler is occupied 1.5-2W, lasers occupy 0.5W, TIA occupied a part, then left to the modulator driver there is not much left.

At the same time, Menara Networks has implemented the optical transmission network (OTN) of ITU-T in the XFP application in the form of specific integrated circuit (ASIC). OTN used in adding optical performance monitoring function and transmitting error correction, at the same time, for signal transmission package. Through the integration of OTN in the plug-in package, package, the functions of signal package, achievable rate and optical signal management can be added to the IP routers and carrier Ethernet switch routers. This design has several advantages: the elimination of the needs of using additional 10 Gbps transponder to transmit switch or router signal (for DWDM transmission), and allows system suppliers to develop universal card without support OTN. But the biggest technical problem for Menara is the development of the included software rather than the development of OTN ASIC.

Plug-in type and Optical Engine

CFP is applicable to the data centre, but the high density applications such as link switch and high performance computing require a more compact design, such as QSFP, CXP and the so-called optical engine.

QSFP is favored interface by the active cable, also is one of the alternative options for copper interconnects. The QSFP transceiver support Quad Data Rate (QDR) 4xInfiniband, can extend the copper cable 4×10 Gbps Ethernet achievable rate of outside 7m. It is also one of the options for more compact 40 GbE short distance interface.

Achieving 100 GbE in QSFP is also a problem, because how to meet the QSFP power limits while adding a 25 Gbps / channel interface and a number of high-speed lasers is quite a headache problem, may need a intermediate package of level definition.

While CXP is a front panel interface can realize more intensive interface in the data centre, is particularly useful for the links between chassis. According to Avago Technologies, the Infiniband is the first target market for CXP, but before CXP transceiver applied in the 100 GbE Ethernet there are several technical problems need to solve, for example, to meet the requirements of IEEE optical specifications.

For optical engine, for example, SNAP12 parallel optical module can be used to connect a plurality of platforms of large-scale IP router configurations, as well as for high-end computing. However, this module is not a plug-in package, is composed of 12 independent channel transmitter and receiver modules, with 6.25 Gbps / channel data rate.

CXP and SNAP12 own self-advantages, such as SNAP12 located on the motherboard and its small package makes it possible to set up next to the ASIC. For those who use optical engine to reduce the cost of parallel interface and meet the requirement of high-speed interface between the motherboard, frame and system, this kind of method just fits its meaning.

100 GbE as well as the arrival of more high-speed era, plus 25 Gbps electric interface will further promote the development of optical engine. But in the standard FR4 printed circuit board to route 10 Gbps is very difficult, and longer link (up to 10 inches) need to use pre-emphasis, electronic dispersion compensation and retiming techniques.

Fibre optic transceivers may be deal with the surge network traffic, but the functions like link platforms, panels and board equipments are the play space where fibre optical transceiver supplier can achieve product differentiation.

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