5 Gbaud QPSK coherent transmission in the mid-infrared

Ozoliņš

Jia

et al. 2022

J. Lightwave Technol.

Since about one and half centuries ago, at the dawn of modern communications, the radio and the optics have been two separate electromagnetic spectrum regions to carry data. Differentiated by their generation/detection methods and propagation properties, the two paths have evolved almost independently until today. The optical technologies dominate the long-distance and high-speed terrestrial wireline communications through fiber-optic telecom systems, whereas the radio technologies have mainly dominated the short-to medium-range wireless scenarios. Now, these two separate counterparts are both facing a sign of saturation in their respective roadmap horizons, particularly in the segment of free-space communications. The optical technologies are extending into the mid-wave and longwave infrared (MWIR and LWIR) regimes to achieve better propagation performance through the dynamic atmospheric channels. Radio technologies strive for higher frequencies like the millimeter-wave (MMW) and sub-terahertz (sub-THz) to gain broader bandwidth. The boundary between the two is becoming blurred and intercrossed. During the past few years, we witnessed technological breakthroughs in free-space transmission supporting very high data rates, many achieved with the assistance of photonics. This paper focuses on such photonics-assisted freespace communication technologies in both the lower and upper sides of the THz gap and provides a detailed review of recent research and development activities on some of the key enabling technologies. Our recent experimental demonstrations of highspeed free-space transmissions in both frequency regions are also presented as examples to show the system requirements for device characteristics and digital signal processing (DSP) performance.

Section: ) Wavelength Conversion Approachmentioning

confidence: 99%

Bridging the Terahertz Gap: Photonics-Assisted Free-Space Communications From the Submillimeter-Wave to the Mid-Infrared

Ozoliņš

Jia

et al. 2022

J. Lightwave Technol.

“…Several MIR FSO transmission demonstrations have been reported based on the wavelength conversion approaches, which up-convert the optical wavelength at the transmitter and downconvert it at the receiver [4]- [7]. Based on such a nonlinear process, up to 10 Gbps single-channel transmissions are demonstrated with in-phase and quadrature (IQ) modulated signals [8], [9]. Very recently, by extending this approach with multidimensional multiplexing techniques, MIR FSO transmissions with an aggregated data rate of up to 300 Gbps are demonstrated [10].…”

Section: Introductionmentioning

confidence: 99%

Direct Modulation and Free-Space Transmissions of up to 6 Gbps Multilevel Signals With a 4.65-$\mu$m Quantum Cascade Laser at Room Temperature

Schatz

Joharifar

et al. 2022

J. Lightwave Technol.

A roadmap for future wireless communications is expected to exploit all transmission-suitable spectrum bands, from the microwave to the optical frequencies, to support orders of magnitude faster data transfer with much lower latency than the deployed solutions nowadays. The currently under-exploited mid-infrared (mid-IR) spectrum is an essential building block for such an envisioned all-spectra wireless communication paradigm. Free-space optical (FSO) communications in the mid-IR region have recently attracted great interest due to their intrinsic merits of low propagation loss and high tolerance of atmospheric perturbations. Future development of viable mid-IR FSO transceivers requires a semiconductor source to fulfill the high bandwidth, low energy consumption, and small footprint requirements. In this context, quantum cascade laser (QCL) appears as a promising technological choice. In this work, we present an experimental demonstration of a mid-IR FSO link enabled by a 4.65-µm directly

“…Several mid-IR FSOC demonstrations have been reported by using nonlinear frequency conversion between 1.55 μm and the mid-IR wavelength before and after the free-space link; in such a way the telecom band laser sources and detectors can be directly used, and high data rates are supported. [10][11][12][13][14][15] However, the high-power requirement and the large size of the nonlinear wavelength conversion modules hinder their practical applications. And in the long run, semiconductor lasers directly emitting at the desirable wavelength are favorable for compact FSOC transceivers.…”

Section: Introductionmentioning

confidence: 99%

Free‐Space Communications Enabled by Quantum Cascade Lasers

Physica Status Solidi (a)

Ozoliņš

Westergren

et al. 2020

Future generations of wireless communication systems are expected to support orders of magnitude faster data transfer with much lower latency than the currently deployed solutions. Development of wireless transceivers of higher bandwidth, low energy consumption, and small footprint becomes challenging with radio frequency (RF) electronic technologies. Photonics-assisted technologies show many advantages in generating signals of ultrabroad bandwidth at high carrier frequencies in the millimeter-wave, terahertz, and IR bands. Among these frequency options, the mid-IR band has recently attracted great interest for future wireless communication due to its intrinsic merits of low propagation loss and high tolerance of atmospheric perturbations. A promising source for mid-IR freespace communications is the semiconductor quantum cascade laser (QCL), which can be directly modulated at a high speed and facilitates monolithic integration for compact transceivers. Herein, the research and development of QCL-based freespace communications are reviewed and a recent experimental study of multigigabit transmission with a directly modulated mid-IR QCL and a commercial off-the-shelf IR photodetector is reported on. Up to 4 Gb s À1 transmission of two advanced modulation formats, namely, four-level pulse amplitude modulation (PAM-4) and discrete multitone (DMT) modulation, is demonstrated.