An efficient, reliable, and reproducible technique to design and manufacture a seven-core fiber (SVF) for utilization in high-performance, integrated optical and optical-based electronic systems/devices are demonstrated in the study published in the journal ACS Photonics.
Study: Ultracompact Multicore Fiber De-Multiplexer Using an Endface-Integrating Graphene Photodetector Array. Image Credit: Es sarawuth/Shutterstock.com
Multicore Fibers - Why are They So Important?
To increase the transmission capacity and capability of optical fibers, space division multiplexing (SDM) transmission-based systems with multicore fibers (MCFs) are now being integrated into currently employed systems.
The transition to multicore fibers is because the spectral densities associated with standard single-mode fibers (SSMF)-based systems are slowly approaching Shannon limits.
A multicore fiber contains numerous cores within a single cladding. Due to these cores, the multicore fiber has a higher transmission capacity than a standard single-mode fiber.
Multicore fibers are extremely essential to SDM as they provide a solution to enhance fiber density with downscaled systems.
Multicore fibers have been extensively researched for high-volume optical-based transmission, sensor development, imaging, and numerous other purposes.
Challenges of Multicore Fibers and How to Tackle Them
In any multicore fiber system, a standard demultiplexer unit necessitates the transformation of multicore fibers into numerous SSMF (referred to as fan-in/fan-out units). These fibers are subsequently linked to their respective infrared-based photodetectors. The result of this whole process is a complicated system with a huge footprint, substantially high energy requirements, and exorbitant costs.
To address this issue, integrated multicore fiber devices such as on-chip grating coupler matrices to substitute fan-in/fan-out units and 2D photodetector matrices on chips as compressed terminal photoreceivers have been explored.
These strategies, however, take on the task of enhancing coupling efficacy and orientation tolerance amid various sets of chips and fibers. In addition, thorough, in-line, low loss-based analyses on multicore fiber systems have still not been properly performed.
A New Technique Enters the Fray
Incorporating optical-based electronic substances, particularly 2D substances which are as thin as atoms, onto fibers is a unique concept that has lately proven to be an efficient method to resolve the restraints intrinsic in silica-based fibers.
End-face optical-based electronic devices, like on-chip setups, have been fruitfully validated using a variety of substances and device constructions. For example, photodetection incorporating elevated performance, 2D substances, and their respective stacked nanostructures have been integrated on the end-faces of the fiber, microfibers, and D-shaped strands.
On the downside, current compatible development techniques make it difficult to realize intricate electrode nanostructures on fibers, limiting any future applications.
To fabricate sophisticated electrode nanostructures on the nanosized end-faces of an individual fiber, the standardized preparation process must be optimized for unique optical fibers, including multicore fibers.
Seven Core Fiber (SCF)
In this paper, the team developed an extremely compact seven-core fiber. Here, they encompassed a chemical vapor deposition-based mono-layer graphene photodetector matrix onto an end-face of a fiber with a tailored electron beam lithography-based method. The aim was to help overcome the issue associated with the irregular form of the fibers while maintaining adequate manufacturing characteristics.
The electrode setup was greatly simplified by employing seven-channel cathodes/anodes and a single mutual electrode, resulting in a highly asymmetrical nanostructure.
The device's photodetection of the seven cores is enabled by the effective photocarrier splitting at the built-in electrical field through the doped intersection in the single-layer graphene.
Single-layer graphene's high transparency provided the device with more than 96 percent transmission ability, aiding in-line and instantaneous light-based status analysis. The device's nanosized framework, which shrinks a conventional clunky fan-out unit and multiple photodetectors to the micro-scale with atomic-sized thickness, could open avenues for fully incorporated optical and optical-based electronic devices with a wide range of applications.
Conclusions
The team presented an extremely compact end-face incorporated multicore fiber demultiplexer centered on a single-layer graphene matrix. The electrode array's enhanced design assures fast response at zero-bias operation, enabling low energy consumption. Furthermore, the team highlighted that a wide range of 2D substances with photo-responses to infrared radiation could be attractive alternatives to use instead of graphene.
With the benefits of a nanosized device volume, enhanced transparency, negligible energy consumption, and marginal cost, the all-fiber photodetector demonstrated by the team opens avenues to elevated performance, and fully incorporated optical and optical-based electronic systems.
Reference
Xiong, Y., Xu, H. et al. (2022). Ultracompact Multicore Fiber De-Multiplexer Using an Endface- Integrating Graphene Photodetector Array. ACS Photonics. Available at: https://doi.org/10.1021/acsphotonics.2c00367
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