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Nguyễn Gia Hào

Academic year: 2023

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2-channel NRZ-OOK modulated optical transmission system with 10 Gbit/s transmission rate per channel and flexible channel spacing. Simulation scheme of 2-channel NRZ modulated optical transmission system with 10 Gbit/s transmission rate per channel with flexible channel interval. BER dependence on channel spacing for a 40 km 2 channel NRZ-OOK modulated optical transmission system with 10 Gbit/s transmission rate per channel.

Evaluation of PAM-4, NRZ and duobinary modulation formats performance in WDM-PON system architecture

Simulation scheme of 8-channel 20 Gbit/s transmission speed per channel PAM-4, DB and NRZ modulated WDM-PON optical transmission system. Eye diagrams of received (a) PAM4, (c) DB and (e) NRZ signals after B2B transmission, and after maximum transmission distance: (b) 50 km with PAM-4, (d) 62 km with DB, (f) ) 27 km with NRZ modulated signals for 8-channel 20 Gbit/s per channel WDM -PON transmission system.


One of the key ingredients at the heart of the communication technologies of the last century has been wireless communication. This work is aimed at improving the performance of coherent FSO communication systems in the presence of atmospheric turbulence. links. One of the most critical steps in efforts to mitigate the performance degradation of optical communications systems is accurate modeling of the.

The lognormal distribution is one of the most commonly used for weak atmospheric turbulence distribution. We design and evaluate the performance of space-time trellis code with two broadcast antennas for FSO channel. With proper modifications of the values ​​of ξ, Eq. 14), can be modified for general cases as well as specific non-orthogonal space-time codes for coherent free space optical communication system.

This section presents the results of the space-time code technique for reducing turbulence-induced fading in coherent FSO communication systems. Free-space optical systems often suffer from blurring and aiming errors, and the effect of the latter has been well addressed [23]. For coherent optical communication links in free space, we investigate the space-time approach to reduce turbulence-induced blurring, which remains a serious performance degrading factor for FSO systems so far.

Space-time codes for MIMO ultra-wideband communication and MIMO free-space optical communication with PPM.


In this chapter of the book, we discuss the most important applications of phased LCoS SLM for optical telecommunications purposes and the use of SLM technology in photonic integrated circuits (PICs) (e.g., field-programmable silicon photonic (SiP) circuits and integrated SLM applications to create versatile reconfigurable elements). Keywords: spatial light modulator (SLM), liquid crystal silicon (LCoS) SLM, optical transformations, computer generated holography (CGH), photonic integrated circuits (PIC), spatial division multiplexing (SDM). Nevertheless, the MCF implementation is susceptible to and can be limited by transmission disturbances such as nonlinearities and core-to-core cross-talk (XT) between signals in adjacent cores that may be represented over multiple optical paths.

This can have a significant effect on system performance in terms of transmission range and network size [16, 17]. Due to SLM support for dynamic reconfiguration of optical wavefronts, it can be used for core-mode multiplexing and demultiplexing. The PIC can be generally characterized as a multiport device with an integrated system of optical elements such as attenuators, modulators, multiplexers, detectors, lasers and optical amplifiers that are embedded on a single chip using a waveguide (WG) architecture [23] .

This can be attributed to tight three-dimensional (3D) alignment tolerances to ensure accurate light coupling. As mentioned above, based on the support for dynamic light reconfiguration, SLM can be used for optical testing and characterization of the PIC, exploring this feature in the supply and/or receiving the optical signal in the PIC [8, 23].

Spatial light modulator (SLM)

This can be realized in a transmissive form using a liquid crystal display (LCD) SLM technology or in a reflective form using LCoS SLM technology. One of the leading features of the modulators is the alignment of liquid crystal molecules. Consequently, with suitable polarizing optics, this affects the incident light beam properties, which can be effectively changed, i.e. amplitude, phase or their combination.

Moreover, it is an electrically addressed reflection modulator category, where a direct and accurate voltage controls the liquid crystal, and the light beam wavefront can also be modulated [ 28 , 29 ]. CGH can be used for various communication purposes and has gained application in indoor visible light communication systems [31]. Furthermore, suitable holograms can be easily generated by applying a number of optimization techniques, such as iterative Fourier transform algorithm (IFTA linear Fourier transform (i.e., linear phase mask-simulated annealing [36]);

Its use in the core component of the WSS system can be attributed to a number of advantages such as greater spatial bandwidth, greater port availability and improved resolution, as well as system miniaturization. It has been observed that ROADM is one of the promising schemes that can be used to improve the traffic capacity of existing and future telecommunication systems [40, 45].


CGH pattern establishment

A linear phase mask can be described as a numerical information transformation (in the Fourier domain) of the input function of interest [25], which can be introduced into the optical system through an SLM. CGH implemented with a linear phase mask can be expressed in the frequency domain as expressed in Eq, where f x and f y denote the spatial frequency vector components corresponding to the image to be generated in the X and Y axes, respectively, and c x and c y represent the horizontal and vertical slope parameters. The option to save or replace the phase mask file is also made available, as depicted in the Phase Mask GUI panel from Figure 4.

In an attempt to realize the hologram that can appropriately replicate the output signal, we evaluated the beam hologram through only the image phase information of the generated hologram. Thus, a first linear phase mask is generated to produce the expected initial field, i.e., the input function of interest. To address these challenges and obtain the desired hologram with an error factor δ ≤ 10%, we implemented an iterative algorithm to optimize the generation of the linear phase mask.

The algorithm is implemented to generate a hologram that replicates the output of the four waveguides (WG) of an optical chip for data compression. The error factor (δ) is defined to quantify the generated hologram deviation from the optical chip expected output [8, 23].

CGH generation setup

Acquire the recurrence field of the hologram generated by SLM (I SLM) with a camera and feed this data to the algorithm. Calculate the difference between the generated hologram and the initial expected field, defined as error factor: δ = |I SLM − I 1 | ≤0.1. If the condition δ ≤ 0.1 is not met, repeat steps ii–iv by iteratively adjusting the values ​​of a 1−4 to compensate for the error factor.

Two different setup arrangements were implemented to create CGH for SDM (e.g., MCF) and PIC applications. After the adjustments, a MCF of 10 m length and a bit error rate (BER) tester were introduced into the setup, as depicted in Figure 6. This signal was injected into the tunable direct modulator laser to create 10 Gb/s optical signal.

After the MCF, the signal was detected by an avalanche photodiode (APD) receiver inside a small form factor transceiver (SFP). In order to eliminate the phase distortion and enable the full scale Fourier transform with the focal length factor ( f ), the optical system is designed based on the 4f system configuration.

Results and discussion

SLM platform for MCF

Future work will be performed to optimize the current convergence, namely the improvement of the optical system components (e.g. lenses and collimator) and the implemented phase masks [18].

CGH for PIC applications

Calculate the intensity integration of the image matrix, i.e. the sum of all elements along each line of the image matrix, depicted as S raw. Application of the Savitzky-Golay (SG) filter to smooth the intensity integration signal obtained in step (1), depicted as S SG. Results of the integrated repetition field intensity profile after the CGH optimization, i.e., after step (3), are shown in Figure 10.

The deviation values ​​(δ) between the generated holograms (i.e., initial I1 and optimized Iout), compared to the expected output from the optical chip (i.e., d1, d2, and d3 from Figure 8), are shown in Table 1 [23]. The measured power of the beams obtained by the integration intensity profiles is depicted in Table 2 [23]. A possible approach to correct some of these artifacts could be the use of Gerchberg-Saxton [37] or simulated annealing [36] algorithms; nevertheless, due to the power loss (up to 9 dB [26]) associated with these approaches, they were not addressed in this implementation [23].

The phase mask that replicates the expected output of the PIC optical operation can be used to multiplex/demultiplex the resulting output. Thus, a proof of concept of PIC operation through the SLM coupling framework [8, 23] is expected.


This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/. by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided that the original work is properly cited. . Outage probability of multi-user mixed RF/FSO relay schemes for heterogeneous cloud radio access networks (H-CRAN). FSO Relay Networks for Performance Improvement in Cloud Computing-Based Radio Access Networks (CC-RAN).

Spatial division multiplexing in data center networks: For multi-core fiber solutions and interconnect-oppressed resource allocation. Multicore fiber interferometer using spatial light modulators for measuring inter-core array index differences. An iterative Fourier transform algorithm for digital hologram generation using only phase information and its implementation in a fixed-.

OFC/NFOEC 2007—Conference on Fiber Optic Communications and the National Fiber Optic Engineers Conference; 2007; p.p.

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