Design of Lengthy Distance Transmission System
After finishing the design of the RS codec and the customized information body encapsulation module and the design of the gigabit charge error correction system, with a view to take a look at the efficiency of the designed system, this paper builds a long-distance transmission system to check the acquire of the system.
The take a look at system consists of BERT, FPGA board, 10G SFP+ LR optical module, 10G SFP+ DWDM module, Pre-Amplifier (PA), Digital Variable Optical Attenuator (EVOA), demultiplexer Wait. The BER tester is an atypical Gigabit Ethernet tester. The white mild and colour mild modules are home optical modules with a transmission charge of Gigabit and receiving threshold of -32dBm. The PA acquire is 35dB
The BERT information enters the shopper aspect of the FPGA board via the white mild module, and after being encoded by the FPGA and packaged with a customized body, the optical sign is distributed via a laser with a wavelength of 1556.55nm. The optical sign is attenuated by the EVOA, and the attenuated sign is handed via the PA to make sure that the output optical energy is fixed, in order that the incoming optical energy just isn’t decrease than the acceptance threshold of the optical module. After the customized body is decapsulated on the aspect, the RS decoder is used for decoding and error correction. After recovering the right Ethernet message, the information is looped again to the BER via the shopper aspect.
Take a look at Outcomes and Evaluation
This paper first assessments a long-haul system with out FEC acquire. The change of optical signal-to-noise ratio is simulated by adjusting the worth of EVOA.
From the desk beneath, we will conclude that the hyperlink with out FEC perform, when the facility of the PA optical port is -42.06dBm, hangs up for two minutes and no bit error happens, however when the facility of the PA optical port is -42.51dBm, there’s a bit error, indicating that the hyperlink The restrict worth energy of the PA incident mild with out error code is about -42.06dBm.
|PA in(dBm)||BER||Timing Interval (min)|
Activate the FEC perform, use the adjustable attenuation to degrade the efficiency of the hyperlink, and measure the corresponding relationship between the PA incident energy and the BER, the corresponding relationship is proven within the following desk.
|PA in(dBm)||BER||Timing Interval (min)|
from the above desk that the BER is zero when the PA incident optical energy is -47.65 when the timing is 2 minutes. By evaluating the optical port energy, we all know that the enter optical energy threshold of the hyperlink is lowered by 5.59dBm. When the bit error charge exceeds the error correction threshold, the BER rises sharply, and even deteriorates in comparison with the traditional sign with out FEC, which can be in keeping with the character of the RS code.
When the long-distance transmission system with out FEC perform is used, the BER reveals a sluggish and steady growing development with the continual lower of the incoming optical energy. When the incoming optical energy will increase to -47dBm, the BER reaches 3.39e-02. Within the long-distance transmission system with the FEC perform, we will get that the BER drops sharply when the incoming optical energy is -48.16dBm, indicating that the RS code performs error correction processing, and the BER is zero when the incoming optical energy is -47.65dBm. By way of the evaluation, it may be seen that FEC has a big impact in bettering the BER of the system.
When the minimal incident optical energy of the system with FEC doesn’t have a BER, the BER of the system with out FEC right now is bigger than 3.39e-2, which is sort of completely different from the RS code simulation in Part 2.4. The low signal-to-noise ratio within the channel attenuation results in misjudgment of the inner information restoration of the SERDES, and the model with out FEC will discard the present body after it can not detect the Ethernet preamble of the present body, which makes the BER of the system rise quickly. Because the program containing FEC detects fixed-length frames, and solely discards the message when the body header just isn’t detected 5 occasions in a row, the message won’t be discarded when the preamble inside 5 occasions is mistaken, however error correction processing might be carried out, therefore the system BER with out FEC will seem like greater than the theoretical BER.
By way of the take a look at of the designed RS codec and customized body encapsulation module, the RS codec’ efficiency is secure, the information hyperlink charge can attain gigabit and the coding acquire can attain at the least 5.5dB, which meets the anticipated design targets.
On this paper, the designed RS codec and customized body module are mixed to kind a gigabit charge error correction system, and a long-distance transmission take a look at platform is constructed to check the designed system. The take a look at outcomes present that the RS codec can present the complete chain. The acquire of greater than 5.5dB within the channel mainly achieves the anticipated design aim.