Coherent frequency tuneable thz wireless signal generation using an optical phase lock loop system

Abstract

Abstract-We experimentally demonstrate, for the first time, the photonic generation of a continuous tunable THz wireless signal based on using optical phase locked loop (OPLL) subsystem and optical frequency comb (OFC). The OPLL is employed to select one optical tone out of optical comb and shift it by desired frequency offset allowing for the frequency tuneability of THz carrier signal. The selected optical tone from OPLL is heterodyned mixed with another selected optical tone of the optical comb to generate a stabilized THz frequency carrier with a low phase noise. The proposed setup is demonstrated by transmitting wirelessly a THz signal modulated with 10 Gbaud QPSK filtered with square root raised cosine (SRRC) at 0.1 roll off factor. The system performance is evaluated for four tuned THz carrier frequencies by changing the wavelength of the laser included in the OPLL. This configuration is a promising architecture that would allow a THz carrier to be flexibly generated at the central office with high frequency stability and low phase noise.

Optical Phase Lock Loop as High-Quality Tuneable Filter for Optical Frequency Comb Line Selection

“…The measured phase noise level is lower than that of the phonically generated signal used in the 10-Gb/s transmission link at 120 GHz carrier [43]. To demonstrate that this OPLL can be used for high-data-rate coherent communication applications, a wireless link with a carrier frequency tuneable between 229 GHz and 244 GHz was successfully demonstrated and described in [11].…”

“…1, two OPLL filters are used to provide two highly coherent tones separated by hundreds of GHz which, if heterodyned on a photodiode, would generate a high frequency, broadly tuneable signal. Moreover, an optical modulator could be added after one of the optical comb line filters, allowing for data transmission at carrier frequency beyond 250 GHz [11].…”

“…The process of acquiring spectral characteristics through phase locking may also be advantageous in applications where, for instance, the spectral characteristics of an ultra-stable master laser needs to be transferred onto a number of inexpensive diode lasers [12]. The OPLL, as presented in this paper, would also find applications in coherent communication [11], LIDAR and clock signal distribution. [13], hybrid mode-locked lasers [14], monolithically integrated passively mode-locked ring lasers [15], [16] and quantum dash mode-locked lasers [17] are some examples of thermally stable, monolithic semiconductor based OFCGs with fixed comb line spacing.…”

Photonic systems for tunable mm-wave and THz wireless communications

“…The first one [2], [3], tackles the problem a priori (i.e., at the transmitter) and relays on the generation of an optical frequency comb. A comb is formed by multiple optical wavelengths all equidistant from each other (comb spacing) and all phase locked to each other.…”

Photonic THz Generation using Optoelectronic Oscillator-driven Optical Frequency Comb Generator

“…One simple implementation is the use of a pair of freerunning lasers with a wavelength separation corresponding to the desired RF frequency to be generated, but this approach suffers from frequency and phase fluctuations [1]. In contrast, optical frequency comb (OFC) generators overcome this problem due to their highly phase correlated optical tones with a fixed frequency spacing [2]. By appropriate two comb lines selection, it is possible to generate pure mm-wave and THz signals [3].…”