A scheme of optical frequency thinning based on MZM modulator

The optical frequency dispersion can be used as a liDAR light source to simultaneously emit and scan in different directions, and it can also be used as a multi-wavelength light source of 800G FR4, eliminating the MUX structure. Usually, the multi-wavelength light source is either low power or not well packaged, and there are many problems. The scheme introduced today has many advantages and can be referred to for reference. Its structure diagram is shown as follows: The high-power DFB laser light source is CW light in time domain and single wavelength in frequency. After passing through a modulator with a certain modulation frequency fRF, sideband will be generated, and the sideband interval is the modulated frequency fRF. The modulator uses a LNOI modulator with a length of 8.2mm, as shown in Figure b. After a long section of high-power phase modulator, the modulation frequency is also fRF, and its phase needs to make the crest or trough of the RF signal and the light pulse relative to each other, resulting in a large chirp, resulting in more optical teeth. The DC bias and modulation depth of the modulator can affect the flatness of the optical frequency dispersion.

In summary, the optical frequency generated by this method has stable frequency interval, low phase noise, high power and easy integration, but there are also several problems. The RF signal loaded on the PM requires large power, relatively large power consumption, and the frequency interval is limited by the modulation rate, up to 50GHz, which requires a larger wavelength interval (generally >10nm) in the FR8 system. Limited use, power flatness is still not enough.