By Zhensheng (Steve) Jia, Ph.D., CableLabs; L. Alberto Campos, Ph.D., CableLabs; Haipeng Zhang, Ph.D., CableLabs; Karthik Choutagunta, Ph.D., CableLabs; Curtis Knittle, Ph.D., CableLabs
Optical frequency combs have garnered significant attention in recent years for their transformative potential on how optical communication networks could evolve. Leveraging cable’s fiber access topologies in particular, these unique light sources can provide our industry with a competitive advantage through a common lower-cost optical signal generator for all optical systems. Optical frequency combs are characterized by optical wavelengths with equal frequency spacing and phase coherence, eliminating the need for guard bands between channels and individual wavelength frequency control, allowing operators to densely pack optical carriers. This increased spectral efficiency can help maximize the use of existing fiber infrastructure. [1]. Other benefits include reduced transceiver power consumption and improved system performance through system-level integration and signal processing. The advantages of optical frequency combs are evident in both dense wavelength division multiplexing (DWDM)transmitters and receivers. In transmitters, a single comb generator can replace multiple discrete distributed-feedback(DFB) lasers or external cavity lasers (ECL), simplifying system design and reducing costs. On the receiver side, using a comb as the local oscillator facilitates joint digital signal processing, which in turn reduces receiver complexity and increases phase noise tolerance. These improvements lead to more robust and reliable communication systems. Furthermore, the deployment of frequency combs at network hubs opens up new possibilities for wireless communication. Through photodetection, these combs enable the generation of low-noise millimeter-wave signals. This capability simplifies radio design, provides access to multiple wireless bands with wide bandwidths, and paves the way for true convergence between wired and wireless networks.