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An effective solution to enhance the capacity of an optical‐interconnect link is utilizing advanced multiplexing technologies, like wavelength‐division‐multiplexing (WDM), polarization‐division multiplexing (PDM), spatial‐division multiplexing (SDM), bi‐directional multiplexing, etc. On‐chip (de)multiplexers are necessary as key components for realizing these multiplexing systems and they are desired to have small footprints due to the limited physical space for on‐chip optical interconnects. As silicon photonics has provided a very attractive platform to build ultrasmall photonic integrated devices with CMOS‐compatible processes, in this paper we focus on the discussion of silicon‐based (de)multiplexers, including WDM filters, PDM devices, and SDM devices. The demand of devices to realize a hybrid multiplexing technology (combining WDM, PDM and SDM) as well as a bidirectional multiplexing technologies are also discussed to achieve Peta‐bit optical interconnects.

Radio over free space optics (Ro-FSO) innovation saddles the vast limit of optical fiber and the portability from local to remote systems. To enhance the capacity of Ro-FSO systems without compromising the bandwidth, this work incorporates use of hybrid polarization division multiplexing (PDM) with optical code division multiplexing (OCDMA) schemes. Due to low deployment time and support cost, the vast majority of the current optical network application systems adopts free space optics (FSO) as the elective answer for suitably supplanting fiber optical cable. This study has incorporated PDM and OCDMA schemes to design a 50 Gbps Ro-FSO link. Ten channels, each with 5 Gbps of data, are transported via FSO link of 3500 m. In addition, the proposed PDM-OCDMA-Ro-FSO link is evaluated under various atmospheric commotions.

An orthogonal frequency division multiplexed-radio over free space optics (OFDM-RoFSO) communication system with dual multiplexing is proposed. Eight input data streams are transmitted simultaneously by using wavelength division multiplexing (WDM) at level 1 and polarization division multiplexing (PDM) at level 2. Input data streams 1–4 and 5–8 are assigned with same set of carrier frequencies i.e. 193.1 THz, 193.3 THz, 193.5 THz and 193.7 THz and separate polarization levels ( and polarized) before transmitting through RoFSO link. A total data rate of 160 Gbps (4 × 2 × 20 Gbps) is achieved in this design. With proposed system, channel performance is evaluated under the influence of atmospheric attenuation and turbulence conditions while measuring system BER, Q-factor, SNR and received power etc. The effect of channel crosstalk is analysed for WDM-PDM dual multiplexed design while considering single input single output (SISO) and multiple input multiple output (MIMO) FSO configurations. The overall analysis predicts that a higher transmission rate and improved capacity levels can easily be achieved with dual multiplexed system.

A comprehensive design is proposed for alternate mark inversion (AMI)-encoded free-space optical (FSO) communication system by hybridizing polarization division multiplexing (PDM) with wavelength division multiplexing (WDM) and its performance is investigated under diverse weather conditions. The WDM transmitter comprises eight channels transmitting 320 Gbps data over the atmospheric turbulent channel considering gamma–gamma (G–G) distribution for the FSO channel model. A PDM-WDM technique not only maximizes the link capacity of the FSO system but also enhances the spectral efficiency (SE) of the system. Besides, the proposed hybrid AMI-PDM-WDM FSO system performance is compared with the traditional AMI-WDM-PDM and AMI-WDM models to demonstrate the advantages of our proposed model for the design of FSO link. It is observed that our proposed hybrid system exhibits excellent performance under diverse weather conditions over the traditional models in terms of Q factor, received optical power, bit error rate (BER), eye diagrams and optical signal-to-noise ratio (OSNR).

A novel ultra-high capacity free space optics (FSO) link has been developed by incorporating hybrid wavelength divison multiplexing (WDM)-polarization division multiplexing (PDM)-orthogonal frequency division multiplexing (OFDM) techniques with 16-level quadrature amplitude modulation (16-QAM) signals. Coherent detection is employed to enhance the receiver sensitivity in the presence of channel effects. The proposed link is analyzed under the impact of dynamic weather conditions viz. haze, rain, dust and fog using bit error rate, optical signal to noise ratio, error vector magnitude and maximum transmission range performance metrics. Sixteen independent DWDM channels with 0.8 nm channel spacing each carrying 100 Gbps data are successfully tranported using the proposed FSO link realizing a net data rate of 1.6 Tbps. Furthermore, we demonstrated a performance comparison of the link with contemporary works. The proposed FSO link provides a feasible and viable solution to implement ultra-high-capacity wireless transmission networks for last-mile access.

A comprehensive design is proposed for free-space optical (FSO) communication system by hybridizing polarization division multiplexing (PDM) with wavelength division multiplexing (WDM) and its performance is investigated under diverse turbulent weather conditions of Bangladesh. Here we consider gamma–gamma (G–G) distribution for the turbulent FSO channel model. Moreover, a PDM-WDM technique not only maximizes the link capacity of FSO system but also enhances the spectral efficiency (SE) of the system. Besides, the performance of this hybrid PDM-WDM FSO system is compared with the traditional model and the proposed hybrid system exhibits excellent performance under diverse atmospheric conditions of Bangladesh. Performance analysis of the proposed model as well as the comparison with the traditional model is described in terms of optical power spectrum (OPS), optical signal to noise ratio (OSNR), bit error rate (BER), Q factor, constellation diagrams, and eye diagrams.

This paper introduces a 400 Gbps free space optics (FSO) system to meet the expected surge in the demand for data traffic. The proposed system is based on using 4-level pulse amplitude modulation (PAM-4) signals in addition to polarization division multiplexing and orbital angular momentum (OAM) multiplexing schemes. To reduce spectrum usage, only a single wavelength of 1550 nm is used. A 400 Gbps is transmitted over two polarization states and eight OAM beams. The signal on each polarization carries the data of four different OAM beams ( LG 0 0 , LG 15 0 , LG 40 0 , and LG 80 0 ). The performance of the proposed model is examined under the influence of light haze, medium haze, heavy haze, low fog, medium fog, heavy fog, wet Snowfall, dry snowfall, light dust storms, medium dust storms, and heavy dust storms. The maximum transmission range and the Bit Error Rate (BER) are used for evaluating the system performance. The simulation results reported the longest FSO link with ranges from 800 to 1475 m under haze conditions. A slight decrease in these ranges is achieved under fog conditions (ranges from 450 to 859 m). The FSO highest attenuation is experienced for HDS case, which results in the shortest range of 73 m. These ranges are calculated at BER Forward Error Correction limit of 3.8 × 10 –3 . Subsequently, the proposed system can be used for the next 6G applications due to its simplicity in design and high transmission capacity.

We propose a silicon polarization-diversity coherent receiver for wavelength-multiplexing transmission without using the large-footprint arrayed waveguide grating (AWG). We have integrated our proposed coherent receiver on the silicon-on-insulator (SOI) platform for high-capacity transmission. In the proposed coherent receiver, high-frequency photocurrent signals from other wavelengths are suppressed by electrical low-pass filters. Moreover, the signal-signal beat interference (SSBI) generated from each wavelength is eliminated by the balanced detection. These two features lend to the proposed coherent receiver being free of the mm-scale AWG. We have demonstrated our proposed coherent receiver to detect a 1.12-Tb/s wavelength-division-multiplexed and polarization-division-multiplexed 16-ary quadrature amplitude modulation (PDM-16-QAM) signal. The compact footprint of the silicon chip promises small-form-factor receivers for future ultra-high-capacity coherent communication systems that require a high integration level and low fabrication cost.

Free space optical (FSO) communication systems are gaining high popularity from the last decade due to its various advantages such as no license spectrum, low-cost implementation etc. In this work, 160 Gbps data is transmitted over 8 km FSO link by adopting alternate mark inversion (AMI), wavelength division multiplexing (WDM) and polarization division multiplexing (PDM) schemes. The results are reported in terms of factor, bit error rate, signal to noise ratio, total received power and eye diagrams.

In free space optical (FSO) communication, the signal performance is mainly affected by suspended dust concentration in atmosphere. The problem is more severe in urban areas, where dust concentration is generally high due to various construction activities, industrial and vehicular pollution. The main pollutants present in atmosphere are PM2.5 and PM10 which depends on size of pollutant. For various dust concentration, the signal performance is analyzed for BER, Q-factor, received power and SNR etc. A dual MUX configuration with MDM-PDM is implemented to enhance channel capacity and data transmission capabilities. The main objective of this work is to analyze FSO link performance for various attenuation conditions in dust environment and to come up with a best possible solution with enhanced channel capacity and link range. A total 80 Gbps transmission at 1550 nm wavelength is implemented while considering an FSO link range of up to 5000 m under dust conditions.