Dispersion Limited versus Power Limited Terahertz Transmission Links Using Solid Core Subwavelength Dielectric Fibers

Abstract

Terahertz (THz) band (0.1 THz-10 THz) is the next frontier for the ultra-high-speed communication systems. Currently, most of communications research in this spectral range is focused on wireless systems, while waveguide/fiber-based links have been less explored. Although free space communications have several advantages such as convenience in mobility for the end user, as well as easier multi-device interconnectivity in simple environments, the fiber-based communications provide superior performance in certain short-range communication applications such as multi-device connectivity in complex geometrical environments (ex. intra-vehicle connectivity), secure communications with low probability of eavesdropping, as well as secure signal delivery to hard-to-reach or highly protected environments. In this work, we present an in-depth experimental and numerical study of the short-range THz communications links that use subwavelength dielectric fibers for information transmission and define main challenges and tradeoffs in the link implementation. Particularly, we use air or foam-cladded polypropylene-core subwavelength dielectric THz fibers of various diameters (0.57-1.75 mm) to study link performance as a function of the link length of up to ~10 m, and data bitrates of up to 6 Gbps at the carrier frequency of 128 GHz (2.34 mm wavelength). We find that depending on the fiber diameter, the quality of the transmitted signal is mostly limited either by the modal propagation loss or by the fiber velocity dispersion (GVD). An error-free transmission over 10 meters is achieved for the bit rate of 4 Gbps using the fiber of smaller 0.57 mm diameter. Furthermore, since the fields of subwavelength fibers are weakly confined and extend deep into the air cladding, we study the modal field extent outside of the fiber core, as well as fiber bending loss. Finally, the power budget of the rod-in-air subwavelength THz fiber-based links is compared to that of free space communication links and we demonstrate that fiber links offer an excellent solution for various short-range applications.

Continuous Fabrication of Microstructured Fibers for THz Communications Using Infinite 3D Printing

“…The inner and outer diameters of the fiber are set to 7.6 mm and 8.0 mm, respectively. The numerical simulation has been carried out using COMSOL Multiphysics in which the refractive index and absorption loss of PP are 1.485 and 2.36 dB/m respectively [1]. As shown in Fig.…”

“…1(d) shows that the maximum bit rate of the signal transmission supported by the printed 2 meter-long fiber. This was estimated using a classic expression Bit rate= 1/4�| 2 / 2 | , while at zero second order dispersion the maximum error-free bit rate is estimated using third order dispersion [1] Bit rate = 0.324/ �| 3 / 3 | 3 , where , and are the propogation constant, angular frequency and fiber length. Theoretically, we therefore estimate that the proposed fiber could support ~20 Gbps error-free bit rate transmission at 2 m-lengths, which is attractive for short-range fiber-assisted communications.…”

“…The experimental characterizations were carried out using an in-house photonics-based THz communication system detailed in [15]. The same system can be used both in the Continuous Wave (CW) THz spectroscopy and THz communication mode by simply disabling or activating the communication unit (see Supplementary Materials Sections S.5 and S.6 for details of the two systems).…”

“…However, by using low-loss polymers (ex. PP) and subwavelength size core, the modal transmission losses can be greatly reduced by pushing the modal field out of the lossy core and into the low-loss air cladding [15,19,35]. This enables the fabrication of high-performance THz waveguides and components for THz communications.…”

Fabrication of Low Loss and Near Zero Dispersion Suspended Core Polypropylene Fibers for Terahertz Communications Using Infinity 3D Printing Technique

“…Moreover, FDM technique became the most fashionable one in directly printing MPWG due to that the wavelength of THz wave is comparable to the printing resolution. In addition, the FDM technique can be applied to variety of polymer materials, such as Poly(methyl methacrylate) (PMMA) [49], Polyethylene Terephthalate Glycol (PETG) [50,51], Acrylonitrile Butadiene Styrene (ABS) [51][52][53][54], Polystyrene (PS) [55,56], Polycarbonate (PC) [57], Polylactic Acid (PLA) [2,58], High Density Polyethylene (HDPE) [59] and Polypropylene (PP) [60,61].…”