We know that the transmission distance of the optical transceiver is determined by many factors, such as wavelength, rate, transmit optical power, receiving sensitivity and a series of indicators, which will affect the transmission rate of the optical transceiver. We have described it in detail in the previous article. elaborate. Recently, a customer asked whether the target transmission distance can be achieved under the specified rate and wavelength? Then I think this problem should be determined by the transmit optical power and receive sensitivity of the optical device. The quality of the optical device determines the transmitted optical power and receiving sensitivity, which also determines the transmission distance of the optical transceiver. First of all, let's explain the parameters of transmitting optical power and receiving sensitivity.
Transmitted optical power refers to the optical intensity at the transmitting end of the optical transceiver, in dBm.
Receive sensitivity refers to the minimum received optical power of an optical transceiver under a certain rate and bit error rate, in units of dBm.
During the transmission process of the optical transceiver, light enters from one end of the optical fiber and is emitted from the other end. Fiber loss will inevitably occur during the entire transmission process, so fiber attenuation is another key factor in the transmission distance of the optical transceiver. The 850nm wavelength is generally used for multi-mode communication. According to the international standard, the optical fiber transmission loss is about 2.5bd/km; the 1310nm wavelength is 0.4db/km; the 1550nm wavelength is 0.2db/km. But this data will also vary according to the quality of the line.
Therefore, before the optical transceiver is put into practical application, we can calculate the longest transmission distance that the transceiver with the transmitted optical power and receiving sensitivity can transmit according to the above data. Here is a simple formula to calculate it:
Transmission distance=|minimum transmit optical power-receive sensitivity|/optical attenuation coefficient
Take the 2.5G 1310 wavelength single-mode optical transceiver as an example:
The optical transceiver adopts 1310 wavelength. Ideally, the optical fiber transmission loss is 0.4db/km, the output optical power is -2~3, and the conventional receiving sensitivity is -24, but this customer requires the receiving sensitivity to be -28.5. After confirmation, our company The highest can be -27. Then calculate with -27, you can get the following results:
Then, based on the receiving sensitivity of -27, our 2.5G 1310nm can transmit up to 62.5km.