Ramachandran said that contributed and invited talks for the subcommittee could be divided into to two main categories: 1) Novel Fiber, and 2) Fiber Applications. The latter represents breakthroughs in engineering, instrumentation, and devices from fiber technology introduced five to fifteen years ago. It is the product of well-tended ideas, hard work, and ingenuity coming into fruition. The former, on the other hand, will likely be the seeds for cutting-edge instruments and systems five to fifteen CLEOs from now. In terms of novel fiber work, Ramachandran discussed two trends 1) Kagome-lattice structures, and 2) Mode-division multiplexing for high-capacity communications.
“We are still developing all sorts of novel fibers. What a fiber is, in terms of being a high-index region that guides light surrounded by a low-index region, is not a settled issue. There are actually a lot of innovations going on.”
Ramachandran spoke of how a decade back, the excitement in fiber research centered around photonic band gap fiber (PBG) which guides light in air (or a structure of silica/air-cores), but still provides many of the properties of standard single-mode fiber, particularly confinement and guidance over many kilometers of length. “That was very exciting, and then what happened afterwards is people found out these band-gap effects are nice for guiding light but they tend to have very small spectral regions where they can guide light, so it is not as universal as our old fibers.”
Kagome-lattice fibers, named for the trihexagonal pattern of air-holes resembling the weave-pattern of a Japanese Kagome basket, may provide one solution to having the versatility of air-guided fibers, while allowing large-bandwidth propagation.
“What Kagome lattice fibers essentially do is solve this spectrum-limiting problem we had with photonic band-gap fibers. You can get huge bandwidth out of these, albeit with slightly higher (theoretical) losses. And so they have been very interesting for doing nonlinear optics of gasses filled in these fibers, to do all sorts of dispersive applications where you need crazy high-bandwidth, and for instance to create plasmas. And then there are people who are trying to make ignition torches with fibers which one would never have thought of doing maybe even five years ago,” said Ramachandran.
The other category for submissions on novel fiber development on this subcommittee has centered on mode-division multiplexing for high-capacity telecom systems. Ramachandran discussed,
“The simplest way to scale information capacity might be to not just use a single mode in a fiber, but to start using multiple modes. And that brings with it a lot of complexities of how different modes interact with each other and what impact dispersion has? What does the area of the fiber do, etcetera, etcetera? Which cycles back to being a fiber design and fiber fabrication problem. So there is a lot of innovation going on there. Even figuring out what modes one wants to send. Are they the standard modes that we have seen in textbooks? Or are they these more exotic orbital angular momentum or vortex modes?”
In addition to contributed submissions in these areas, four of the invited talks concern novel fibers and their propagation effects. On the other hand, the remaining invited talks, tutorial, and contributed submissions focus on fiber applications. The tutorial, by Michael Marhic of Swansea University, U.K. entitled “Fiber Optical Parametric Amplifiers in Optical communications,” will be given on Thursday June 13, from 2:00-3:00 pm. The invited talks in fiber applications, which are indicative of the contributed submissions, comprise topics as diverse as fiber parametric devices, microwave plasmas, gravitational wave detection, mid-IR sensing, and ultrafast laser combs.
Ramachandran notes, “And the interesting thing about that space is the fiber itself that people are using is perhaps something that was developed anywhere between five years ago to maybe even fifteen years ago. We are now beginning to see all the promise that we initially thought that fibers could deliver and actually seeing applications across different disciplines of science and technology.”