Two-way free-space optics-based interface between fibre and 5G communication employing polarisation-orthogonal modulation

5G communication provides a substantial increase in data transmission capacity. FSO-based interface between fibre and 5G communication integrates fiber optics, FSO and 5G communications. A two-way fibre-FSO-5G wireless communication with polarisation-orthogonal modulation is presented and reported.
Like

High data rate, ultra-low latency, and massive connection requirements in 5G services have substantially promoted the development of telecommunications. The development of 5G signals through fibre-FSO-wireless communications (see Fig. 1) has greatly accelerated this global trend. In this demonstration, we report the deployment of two-way fibre-FSO-5G wireless communications using polarisation-orthogonal modulation. By implementing polarisation-orthogonal modulation, the polarisation of the central carrier (x-polarisation) is orthogonal with the optical sidebands modulated with 5G MMW and sub-6 GHz signals (y-polarisation). It shows a 5G communication system with a low-complexity configuration to split the central carrier for upstream carrier and optical sidebands for downstream transmission. The successful establishment of the two-way FSO-based interface between fibre and 5G communication marks a crucial step in the implementation and development of 5G MMW/sub-6 GHz communications. It has a major impact on the integration of fibre optics, FSO, and MMW/sub-6 GHz communications and the use of employing polarisation-orthogonal modulation.

Fig. 1 The development of 5G signals through fibre-FSO-wireless communications.

The architecture of 5G MMW/sub-6 GHz signals through two-way fibre-FSO-wireless communications employing polarisation-orthogonal modulation is demonstrated in Fig. 2. The light sent out from a distributed feedback laser diode is supplied to a Mach-Zehnder modulator (MZM) through a polarisation rotator. The MZM is worked at the minimum transmission point and driven by integrated 1-Gbps/2.2-GHz and 10-Gbps/19-GHz 16-QAM-OFDM signals through the modulator driver. Polarisation rotator rotates the polarisation direction of a polarised light by θ angle. Due to the electro-optical characteristics of LiNbO3 crystal, the half-wave voltage Vπ in the x-direction is approximately 3.58 times larger than that in the y-direction. Owing to higher Vπ in the x-direction, the y-polarised light is modulated as it passes through the LiNbO3 crystal. The x-polarised light, on the other hand, remains unmodulated. Since the MZM is biased at the minimum transmission point, y-polarised light is modulated in an optical carrier suppression form. The y-polarised downstream sidebands are optically converted from a 1-Gbps/2.2-GHz signal to 1-Gbps/4.4-GHz 5G sub-6 GHz signal, and from a 10-Gbps/19-GHz signal to 10-Gbps/38-GHz 5G MMW signal. Whereas the x-polarised light is transmitted and reused as an upstream carrier. For upstream, the x-polarised central optical carrier split by the polarisation beam splitter is reused and modulated by an MZM with integrated 1-Gbps/1.85-GHz and 10-Gbps/13-GHz 16-QAM-OFDM signals. The MZM is worked at the minimum transmission point as well, which leads to the x-polarised upstream light being modulated in an optical carrier suppression form. The x-polarised upstream sidebands are optically converted from a 1-Gbps/1.85-GHz signal to 1-Gbps/3.7-GHz 5G sub-6 GHz signal, and from a 10-Gbps/13-GHz signal to 10-Gbps/26-GHz 5G MMW signal. Over 25-km SMF, 1-km FSO, and 20-m/10-m 5G wireless transmission, sufficiently low BERs and EVMs are obtained for downstream/upstream transmissions.

Fig. 2  5G MMW/sub-6 GHz signals through two-way fibre-FSO-wireless communications.

Figure 3(a) shows the downstream/upstream BERs at different received MMW/sub-6 GHz powers over 25-km SMF, 1-km FSO, and 20-m (MMW)/10-m (sub-6 GHz) RF wireless cascaded-medium. For 10-Gbps/38-GHz and 1-Gbps/4.4-GHz 16-QAM-OFDM signals transport (y-polarisation; downstream), we achieve a 3.8x10−3 (FEC limit) BER at -26.7 and -28.5 dBm received MMW/sub-6 GHz powers, and we attain a 4.7x10−5 (< 3.8´10−3 FEC limit) BER at -24.6 and -26.8 dBm received MMW/sub-6 GHz powers. For 10-Gbps/26-GHz and 1-Gbps/3.7-GHz 16-QAM-OFDM signals transport (x-polarisation; upstream), we achieve a BER of 3.8x10−3 at -27.4 and -28.8 dBm received MMW/sub-6 GHz powers, and we attain a BER of 4.7x10−5 at -25.4 and -27.4 dBm received MMW/sub-6 GHz powers. In addition, the measured EVMs at different received MMW/sub-6 GHz powers are exhibited in Fig. 3(b). Over 25-km SMF, 1-km FSO, and 20-m (MMW)/10-m (sub-6 GHz) 5G wireless transports, the EVMs of four 16-QAM-OFDM signals are less than the 12.5% 3GPP limit as the received MMW/sub-6 GHz powers are higher than -28.7 (y-polarised 10-Gbps/38-GHz; downstream), -29.4 (x-polarised 10-Gbps/26-GHz; upstream), -30.5 (y-polarised 1-Gbps/4.4-GHz; downstream), and -31 (x-polarised 1-Gbps/3.7-GHz; upstream) dBm, respectively.

Fig. 3 Downstream/upstream (a) BERs and (b) EVMs at different received MMW/sub-6 GHz powers.

A two-way fibre-FSO-5G wireless communication system employing polarisation-orthogonal modulation is offered and realized. For downstream transmission, y-polarised intensity-modulated 10-Gbps/38-GHz and 1-Gbps/4.4-GHz 16-QAM-OFDM signals through fibre-FSO-5G wireless communication is practically built. For upstream transmission, x-polarised intensity-modulated 10-Gbps/26-GHz and 1-Gbps/3.7-GHz 16-QAM-OFDM signals transport through FSO-fibre-5G wireless communication is practically constructed. 3.7 and 4.4 GHz carriers are adopted for 5G signal transmission to meet 5G sub-6 GHz frequency band (410 MHz-7.125 GHz) demands, and 26 and 38 GHz carriers are adopted for 5G signal transmission to satisfy 5G MMW frequency band (24.25 GHz-71 GHz) requirements. With an in-depth observation of two-way fibre-FSO-5G wireless communication system, good performance of low BER and EVM are achieved through a distance of 25 km SMF, 1 km FSO, and 20 m/10 m 5G wireless. The successful establishment of the two-way FSO-based interface between fibre and 5G communication marks a crucial step in the implementation and development of 5G MMW/sub-6 GHz communications. It has a major impact on the integration of fibre optics, FSO, and MMW/sub-6 GHz communications and the use of employing polarisation-orthogonal modulation.

Please sign in or register for FREE

If you are a registered user on Research Communities by Springer Nature, please sign in

Subscribe to the Topic

Microwaves, RF Engineering and Optical Communications
Technology and Engineering > Electrical and Electronic Engineering > Microwaves, RF Engineering and Optical Communications
Optical Communications
Physical Sciences > Physics and Astronomy > Optics and Photonics > Optical Communications

Related Collections

With collections, you can get published faster and increase your visibility.

Thermal Engineering for Sustainability

This collection will publish papers on the topic of thermal engineering with a particular focus on applications related to sustainability.

Publishing Model: Open Access

Deadline: Mar 30, 2024

Endoscopy

This cross journal collection on endoscopy brings together technological advances to improve capability, with clinical research exploring procedures and applications.

Publishing Model: Open Access

Deadline: May 09, 2024