Abstract
Anovel dual-stage optical frequency comb (OFC) demultiplexer, for use in a photonic millimeter-wave (mmW) generator, is demonstrated. Unlike other demultiplexing techniques, the proposed method features a single optical path for both tones used for the mmW generation, thus eliminating the challenges related to the mismatch of path lengths. In addition, the use of active demultiplexing provides filtering, amplification and data modulation of the comb tones, all in a single device. In this article, we demonstrate the operational principle of the dual-stage active demultiplexer-enabled mmW generation, verify the quality (beat tone width ∼13 Hz) and stability (power fluctuation ∼0.26 dB) of the generated mmW signal and validate the performance of an A-RoF system employing the proposed device. For the system demonstration, 64-QAM UF-OFDM signals, at frequencies of 29.5 and 38 GHz, are generated and transmitted over 25 km of single-mode fiber. A BER of 3.2e-4 for 29.5 GHz and 1.6e-4 for 38 GHz is achieved without the use of optical amplifiers, showing the great potential of the proposed technique. Finally, a case study of an A- RoF distribution system, employing three different demultiplexing techniques, is presented. We demonstrate that the proposed transmitter, in comparison to other demultiplexing techniques, provides a larger power budget (> 6 dB) that can be used to extend the reach of the system and/or increase the number of remote radio units served using a single OFC.
Highlights
The demand for higher data rates in wireless communications has been increasing over the years; fuelled by the proliferation of the connected smart devices, highdefinition multi-media and cloud-based services
This large power variation stems from the wavelength drift of the optical frequency comb (OFC), which is translated to power variations, as the tones experience different attenuation when passing through the narrow passband of the AWGF
We demonstrated tunable dual-stage demultiplexing with various frequency separations and verified an efficient phase noise transfer from comb to both demultiplexed tones
Summary
The demand for higher data rates in wireless communications has been increasing over the years; fuelled by the proliferation of the connected smart devices, highdefinition multi-media and cloud-based services. To reap the benefits of this new paradigm, network operators need to build an infrastructure capable of supporting the stringent transmission requirements (large bandwidth, low latency, high reliability), in both the wired and wireless domains To satisfy these demands, while minimizing the cost and energy consumption, 5G and beyond will employ a centralized or cloud radio access network (C-RAN) [4], consisting of a pool of baseband processing units (BBUs), connected to the antenna sites or remote radio units (RRUs) by an optical fiber (as depicted in Fig.1) or a mmW link. The generation of mmW signals, at 29.5, 34, and 63.5 GHz, with high purity and exceptional stability is demonstrated The latter is confirmed, by measuring the beat tone linewidth and power fluctuations over 80 minutes.
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