Principle, Design, and Prototyping of Core Selective Switch Using Free-Space Optics for Spatial Channel Network

Abstract

We describe the principle, design, and prototyping of a free-space-optics-based core selective switch (CSS) for spatial channel (SCh) networks (SCNs) in the age of space division multiplexing (SDM). A CSS in an SCN corresponds to a conventional wavelength selective switch (WSS) in a current wavelength division multiplexing network. It incorporates functionalities for spatially demultiplexing SChs from an input SDM port and for switching and multiplexing any of them into any of output SDM ports. We discuss the design for free-space-optics-based CSSs that is applicable to CSSs supporting various numbers of cores per multicore fiber (MCF) and various numbers of MCF ports. We show an example of an implemented 5-core 1 × 6 CSS prototype that integrates an MCF collimator, spatial multiplexer/demultiplexer array, and liquid-crystal-on-silicon spatial light modulator. Although some output MCF ports exhibit relatively high insertion loss (IL), the CSS prototype shows that a CSS will potentially provide low net IL at the level of approximately 2 dB. To verify that there are no unknown deteriorating factors in the CSS prototype, we tested the prototype implemented in a hierarchical optical cross-connect configuration by measuring the pre-forward error correction bit error rate. Spatial bypassing and spectral grooming of a 900-Gb/s SCh employing a CSS-based spatial cross-connect and a conventional wavelength cross-connect are successfully demonstrated with no optical signal-to-noise ratio penalty.

[Retracted] Research on Haze Image Enhancement based on Dark Channel Prior Algorithm in Machine Vision

“…In view of the above problems in fog image enhancement, this paper calculates the dark primary color image based on the dark channel principle [26][27][28][29], optimizes the calculation process of transmittance t(x) and the estimation of atmospheric light value A, and then restores the image to HSV space. In RGB color space, the relationship between the values of the three-color components and the generated colors is not intuitive.…”

Core Selective Switch With Low Insertion Loss Over Ultra-Wide Wavelength Range for Spatial Channel Networks

“…In order to address the above problems in traditional [11,14,16]. The idea behind the approach is based on introducing reasonable connection constraints in the cross-connection part and add/drop part to balance the connectivity flexibility and node complexity, thus node cost, according to the preferences of network operators and over-the-top players.…”

“…Members of our research group recently prototyped a CSS based on free-space optics. It comprises two major optics: arrayed MCFs attached to 0.25-pitch graded-index (GRIN) lenses, which provide both beam collimating and spatial multiplexing/demultiplexing functions, and a liquid-crystal-on-silicon spatial light modulator (LCoS SLM), which serves as a core-by-core switching element [14]. A proof-of-principle experiment was successfully completed using the CSS prototype; however, the prototype exhibited relatively high insertion loss (IL) and high polarization-dependent loss (PDL) that varied depending on the output MCFs.…”

SDM-WDM ROADM Based on Direct-Laser-Writing SDM Core Separator

“…Compared to conventional wavelength division multiplexing (WDM) switching, the introducing of new switching dimension of fiber core may greatly increase the complexity of optical switching nodes, especially for non-blocking cases [8], [9]. To solve this problem, some connection-constrained SDM-WDM reconfigurable optical add/drop multiplexer (ROADM) architectures have been proposed [10]- [14]. For examples, an SDM-WDM switching node can be realized by demultiplexing all the spatial channels to SMFs using FI/FO devices and switching by wavelength selective switches (WSS) supporting large quantity of input/output ports [10].…”

“…Similar functionalities are also achieved by free-space beam steering based on micro-electro mechanical mirrors [13]. Besides, core-selective switching has been proposed based on free-space optical devices such as spatial light modulator [14]. However, these approaches may have different shortcomings such as node complexity, large insertion loss, large inter-core crosstalk or expansibility.…”