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How to choose the right wavelength for the single mode optical module that applied in data center?

Date:2018-11-01 16:31 From:C-LIGHT Onclick:
Generally, the application distance of a single mode optical module applied in data center is more than 500m. For single mode 1310nm and 1550nm are available. How to choose the right wavelength? This is a problem that plagues many people. So first it’s necessary to understand what is most important to the data center.

Many people's answers are operating costs. Where does the operating cost come from?
1. In the early stage, the total cost of purchasing optical modules (unit price * quantity).
2. Late, maintenance costs. Among them, the most considered is the use of electricity. 

How big is the data center power consumption? For example, a data center covering an area of 3,000 square meters uses 21,000 kWh of electricity a day. The first major factor in these electricity charges is the electricity consumption of the equipment itself. The second major factor is the electricity consumption of air conditioners.

Therefore, many data centers will choose to be built in the sea and built in various cool places. In order to save power, the power consumption of the optical module should be as low as possible. To achieve low power consumption of optical modules, lasers, transmission channels, etc. are particularly important.


From the above data:
1. In terms of performance, MZM is better than EML, and EML is better than DML.
2. From the perspective of power consumption, DML saves power compared to EML. EML and MZM are nearly the same.
3. From the price point of view, DML is cheaper than EML, EML is cheaper than MZM. 
Summary: If the DML laser specification meets the usage requirements, it is both cheap and power efficient, so it meets the data center cost requirements.

2) The budget of the transmission channel.
Power budget for transmission = transmitted optical power - receiving sensitivity = fiber loss + dispersion cost + margin.
Summary: To reduce the transmit power, or to reduce the loss and dispersion cost. DML is the most power-saving single-mode option, and power is also associated with power savings.

From the above figure: the wavelength of 1310nm, the loss is large, but the dispersion is small. At a wavelength of 1550 nm, the loss is small, but the dispersion is large.

1. Look at the loss and distance first, short distance (less than 10km), the loss of a few dB is not important, but the dispersion of DML is very important, choose O-band, mainly 1310nm.
2. For 40km, there are 1310 wavelengths, and 1550 wavelengths. This is a gray area.
3. For 80km, the loss becomes very important, so 1550nm is the best choice, then the dispersion should be weighed, DML is cheap, but the dispersion is large, then choose the EML modulation method, and get the loss reduction, but The cost and power consumption are sacrificed.

To sum up:
In a large environment, wavelength / power / loss / unit price / performance ..., is a factor in the overall cost trade-off. For different application distances, choose a different solution. as follows:
1. <500m, with VCSEL, cheap, low power consumption.
2.500m~10km, 1310 DML, cheap, low power consumption, low dispersion, loss is not important. 
3.40km, 1310/1550nm coexist, mainly related to rate, weighing dispersion and loss. 
4.80km, 1550nm, loss becomes an important parameter.

Shenzhen C-light Network Communication Co., Ltd. is a technology company dedicated to the development, production and sales of high-end optical transmission. Product development and research, advanced technology, large production capacity, strict quality control, complete product range, fast delivery and service, product price concessions. The products have obtained the corresponding certification: ISO9001, RoHs, TUV, CE, FCC certification.




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