The fifth plan was amazing.The configuration is Coherent, which is close to the third plan, but here is to use "Self-Homodyne Detection".
SHD itself is a method that has been studied for a long time and is a type of coherent communication.In the case of the third and fourth plans classified as "HD (HD (HD (HD)" HD (HD) ", a continuous light called" LO (LOCAL OSCILLATOR) "is prepared separately from the signal light, and the signal light interferes with the signal light and the LO.Although it is a method of extracting complex amplitude, this signal light and continuous light do not completely match the frequency and phase.
In response, SHD, on the other hand, completely matches the LO frequency and phase completely with the signal light.As a result, the signal sensitivity is improved by 10 to 20 dB, and when the WDM is used, the interference of the adjacent channel can be removed with an ideal filter (after converting it from light to an electric signal), so especially in DWDM, due to wavelength dispersion, etc.There are several significant benefits, such as the ability to compensate for the distortion with an electric circuit.
受信側には、「ICR（Integrated Coherent Receiver）」と「SVDD（Stokes Vector Direct Detection）」を使う2案が上がっている。つまり、複数の提案が出せる程度にまだ鉄板の方式がない、ということでもあるHowever, aside from long -distance transmission systems using DWDM, is it possible to implement at realistic costs only for a system that has never been used in a 10km order "short -range" network?When it is said, there is quite a question mark.
Anyway, the method that uses the SHD is 200g per lane, so it is possible to send and receive one pair of optical fiber by arranging it with four wavelengths and biting the WDM MUX/DEMUX.
ただし、DAC/ADCの数は増えるし、DSPでの処理はさらに重くなると思われる。The difference between this method and the 800g LR4 is that the wavelength can be widened (CWDM can also be used).Because it is in principle strong (or rather, it can be corrected in the DSP stage) for distortion caused by Chromatic Dispersion Limit (or rather can be corrected in the DSP stage), the laser light source can be used, and the WDM MUX/DEMUX is also available.It seems to be cheaper than 800g LR4.
