Design and simulate the demultiplexer using photonic crystal ring resonator for DWDM system

Currently, there is a great need for high-speed networks due to ongoing technological advancements whose main goal is to increase transmission capacity and coverage area (Sharma and Kaur 1280). A smart way to boost the speed and bandwidth of communication and data processing systems is to use optical waves for data and information transmission (Salimzadeh and Alipour-Banaei 2018; Saghaei et al. 2011). Optical waves have a high efficiency of transmission and are less prone to electromagnetic noise. Thus, the communication industry's (Pon et al. 2022) anticipated transition from electronics to optical fiber technology. Furthermore, all communication processes must be carried out in the optical domain in order to benefit from optical communication; as a result, every device employed in the communication network must be entirely optical (Sani et al. 2020a).

All-optical circuits have the potential to be made using photonic crystals (PC), which have proven to be appealing options. The periodic distribution of refractive indices results in photonic band gap areas, which are necessary for focusing and confining optical beams inside the proper waveguides (El-Khozondar et al. 2019; Taya et al. 2019; Noori et al. 2016). By introducing line flaws inside a two-dimensional PhC, optical waveguides can be easily made (Genga 2020). The potential of 2DPhCs for creating optical devices appropriate for all optical communications has been demonstrated (Wang et al. 2016). Additionally, their outstanding abilities in the development of analog and digital (Tavousi et al. 2016a; Tavousi and Mansouri-Birjandi 2017) optical devices, including data converters (Fasihi 2014; Chizari et al. 2016), back grating for solar cells (Tavousi et al. 2016b), Smith-Purcell radiation Bragg graphene filters (Tavousi et al. 2017a), optical filters (Tavousi et al. 2017b; Alipour-Banaei and Mehdizadeh 2017), demultiplexer (Rawal and Sinha 2009; Serajmohammadi et al. 2015; Gupta and Janyani 2014), switches (Mehdizadeh et al. 2017; Teo et al. 2004), logic gates (Bao et al. 2014; Singh and Rawal 2015), adders (Serajmohammadi et al. 2018; Neisy et al. 2017).

PC-based devices can address the speed and complexity challenges related to the electro-optic transformation in conventional digital electronic technologies as the demand for additional traffic rises. These compact, fast, all-optical logic devices provide the foundation for the optical signal processing systems that will power the next generation of optical integrated networks. These devices provide a number of benefits over traditional digital electronics, including flexibility, the capacity to handle wide bandwidths, improved noise immunity, and substantially greater data rates. An all-optical network is one that conducts communication entirely without the need of electronics. Photonic crystals currently offer ideal substrates for the construction of ultrafast, small optical logic devices that will be used in future optical networks (Saranya 2021).

The design of integrated optical circuits has started to incorporate photonic crystals (PCs) more and more recently. These man-made systems that are built from multilayer dielectric materials with different refractive indices can alter how fast light travels. This periodicity results in the formation of a photonic band gap (PBG), which forbids certain directions of light propagation inside the structure. The PBG can be changed by adding defects inside the periodic structure, which has led to the development of numerous optical devices, including optical demultiplexer, Mach–Zehnder interferometers, optical switches, photonic crystal fibers and waveguides (Sani et al. 2020b).

Furthermore, the wavelength division multiplexing (WDM) (Zafar et al. 2019; Wang et al. 2011), dense WDM (DWDM) (Fallahi et al. 2019; Vijayaraj and Arunagiri 2023), and coarse WDM (CWDM) (Zheng 2020; Nurjuliana Juhari et al. 2017) techniques are commonly used in telecommunications networks (Suthir and Janakiraman 2018; Jayashri, et al. 2017; Prabhu et al. 2022) to separate bandwidth into smaller channels. The optical bandwidth is demultiplexer in the receiver to implement the WDM technique in the optical network. Numerous studies and simulations have been conducted on demultiplexer based on graphene, metal–insulator-metal (MIM), arrayed waveguide grating (AWG), and photonic crystals (Moradiani 2020).

The likelihood of DWDM systems being used practically and often increases with higher bandwidths and denser channel spacing. Distortion effects become more noticeable as nonlinear effects worsen with the strength of optical signals transmitted in a network, where the central unit normally broadcasts sufficient enough power to enable transmission above extended distances and decrease the number of repeaters (Roka and Martin 2022).

Figure 1 illustrates the new ring resonator that was created utilizing a photonic crystal ring. The ring resonator structure is made up of rods arranged both vertically and horizontally. The waveguides were used in the design of the RR. When light enters port A, port B and port C output light, accordingly. Port A is the input waveguide, and port C is the drop waveguide. In order to create the ring resonator design, we first designed 13*12 dielectric rods structure. Line and point defects were then used to remove part of the rods. The wavelength range of the source mode is 1500–1600 nm.

Numerous factors, such as transmission efficiency, quality factor, footprint, etc., will be involved in the ring resonator. Rods such as inner, outer, coupling, and scatter are crucial in determining the ring resonator's efficiency. For improved response and light containment, the inner and outer rods are positioned precisely. Scatter rods are positioned at each of the ring resonator's four corners to improve drop efficiency and quality factor. Coupling rods are used to pair light from one waveguide to another. The output of the suggested ring resonator construction, with light confinement on resonance at 1.5328 nm and an off resonance wavelength range of 1.6 nm, is depicted in Fig. 2. With a Q factor of 7840, the suggested RR design has a transmission efficiency of 99.9%. Off resonance is when there is no coupling to the ring and only light travels in the waveguide itself. On resonance refers to how much light is coupled into the ring from the waveguide.

The 1*4 demultiplexer structure is designed using Lumerical tool FDTD (Finite Difference Time domain) method shown in Fig. 3. With dimensions of 198.61µm², this demultiplexer is constructed in the x (42 rods) and y (11 rods) axis. Four drop waveguides, one bus waveguide, four ring resonators, and varying inner rods in each ring resonator to achieve optimal drop waveguide performance comprise the demultiplexer. This ring resonator design will primarily use two types of rods: connection rods and scatter rods. The main purpose of scatter rods is to lower output losses. With proper scatter rod adjustment, they can also yield the best Q factor.

When light enters the bus waveguide from the source, coupling rods are connected and convey the light information to the ring resonator as the light passes through the structure. The information will then be transmitted to the drop waveguide by coupling rods below. Since the demultiplexer is a 1*4, can evaluate the output using a four drop waveguide. Both the bus waveguide and the drop waveguide are intended to remove the rods from each ring resonator vertically and horizontally, respectively. We use line defect for the bus waveguide design and drop waveguide for the ring resonator shape to build the structure. The radius of the inner rods mentioned as Ri₁, Ri₂, Ri₃, Ri₄ for each channel different radius are used to get better efficiency.

As a result, the proposed demultiplexer structure has been square in dimension, which lowers scattering losses and, conversely, increases coupling efficiency. Therefore, it is suggested that the model be used to enhance a number of qualities, including crosstalk, transmission effectiveness, Q factor, etc. For this purpose, the PBG (Photonic band gap) and normalized transmission spectra for the proposed structure are obtained using the Plane Wave Expansion (PWE) and Finite Difference Time Domain (FDTD) methods. The modeling of a single ring resonator construction is first covered in the study, which is subsequently expanded to a four ring resonator structure. The outcomes are evaluated and discussed at the conclusion. In order to determine the resonance wavelength in each drop, the waveguide will receive the output at a specific wavelength. The major factor used to compute the characteristics of the ring resonator structure is the resonance wavelength. The proposed work demultiplexer is constructed in two dimensions, which reduces complexity when compared to three dimensions while producing the same results (Fig. 4). It also produces results that are more effective than one dimension.

By retaining the power monitor at each port, the normalized transmission power of each port is obtained. In a simulation, the time step is crucial to obtaining precise results that accurately reflect the real-world environment. In order to attain a high 'Q' factor, the change in grid sizes in the 'X' and 'Z' directions are fixed at 0.05a = 27 nm. The prerequisite that the step time must meet is:where ∆t—is the step time, and c—is a speed of light in free space.

Four channels having core wave-lengths of 1552.4 nm, 1553.2 nm, 1554.1 nm, and 1555.4 nm can be divided with this demultiplexer. The demultiplexer has a maximum and minimum transmission efficiency of 99.06 and 98.33%, respectively. Our demultiplexer operates in the 1552.4–1555.4 nm wavelength region, and its average Q factor and average normalized transmission efficiency are 7870.90 and 98.76%, respectively.

According to this Fig. 5, the transmission efficiency of the λ₁ = 99.06%, the λ₂ = 96.08%, the λ₃ = 89.24%, and the λ₄ = 99.98%. Following simulation, as seen in Fig. 6, we found modest crosstalk values with a maximum of 15 dB and a minimum of 25.5 dB, demonstrating that the influence of the channels on one another is minimal.

The demultiplexer structure has an overall length of 23.929 μm and a width of 8.3 μm, making a total footprint of 198.61 μm².The demultiplexer transmission efficiency varies with narrow channel spacing, ranging from 98 to 99%. The Q factor also depends on Bandwidth; as bandwidth lowers, the Q factor rises automatically since they are inversely proportional to one another.where λ is the resonance wavelength and ∆λ is the bandwidth (Roka and Martin Mokra.n”, 2022).

The simulation results for the suggested demultiplexer design for each channel are displayed in Table 1. With a bandwidth of 0.22 nm, channel 1 (λ₁) obtained a quality factor of 7056.36, and its transmission efficiency is 99.06%. With a bandwidth of 0.19 nm, the second channel (channel λ₂) achieved a quality factor of 8174.74, and its transmission efficiency is 98.91%. With a bandwidth of 0.18 nm, the Third Channel (λ₃) obtained a quality factor of 8633.89, and its transmission efficiency is 98.77%. With a bandwidth of 0.21 nm, the Fourth Channel (λ₄) attained a quality factor of 7406.67, and its transmission efficiency is 98.33%.

The Crosstalk value for the suggested demultiplexer graph is shown in Fig. 6 as being dependent on the resonance wavelength. The crosstalk value for four channels ranged from − 15 dB to − 25 dB, and the crosstalk graph was shown with regard to the wavelength and transmission (dB scale). Table 2 displays the crosstalk value (dB) between each demultiplexer channel.

Table 3 compares the four channel demultiplexer with previous works and shows how it outperformed them in terms of efficiency, quality factor, and footprint due to its narrow channel spacing. This suggested demultiplexer can be used in the receiver part of a DWDM system to obtain a high quality factor.

In this research, a novel 4 channel demultiplexer for DWDM applications is designed. It is built and simulated utilizing a photonic crystal ring resonator. The demultiplexer was created on a photonic crystal platform employing a single bus waveguide, four drop waveguides, and a ring resonator structure. The transmission efficiency of the demultiplexer, which has a tiny channel spacing of 0.8 nm, is 98.67%. The crosstalk value ranges from − 15 dB to − 25 dB, and the suggested work achieves an average quality factor of 7870.90. Each channel's resonance wavelength range is 1552.4 nm, 1553.2 nm, 1554.1 nm, and 1555.4 nm. For the DWDM application, the suggested demultiplexer has a size of 196.87 µm².