A low-cost high-resolution and low-bend-loss multicore imaging optical fiber (MCIF) has been demonstrated in the R&D Center of High Power Laser Components of Shanghai Institute of Optics and Fine Mechanics (SIOM) of the Chinese Academy of Sciences (CAS). This MCIF comprising of 5000 cores is made of low-cost high-index-contrast commercial silicate glasses, leading to a numerical aperture up to 0.552 at 750nm. The progress is recently published in Optics & Laser Technology under the title of "Bend resident high resolution imaging optical fiber" on September 12, 2022.

As a key component of endoscope, MCIF is regarded as key component of minimized optical endoscope and find essential applications in biomedical imaging and many imaging systems that require lightweight and miniaturization. High resolution, high numerical aperture, low bend loss and low crosstalk are required for high imaging quality by MCIF. The researchers in SIOM applied three-size core design to minimize the crosstalk and selected commercial glasses H-ZK9B and H-K3 for core and cladding materials for high index contract, giving rise to the improved NA and reduced core diameter and core pitch.

The fabricated diameter of a single core of MCIF varies from 1.1 to 1.8um, with a pitch of approximate 2 um. The resolution is characterized better than 4um at 650nm. The outer MCIF diameter is 300 um. The imaging performance is demonstrated no degradation in experiment for bend. When the bending radius is less than 2 cm and the imaging is found unaffected at the wavelength ranging from the visible light to near-infrared, overwhelming the performance of most commercial optical fiber bundle products.

Fig.1. Left: Schematic of multiple-stack-and-draw method; and Right: pictures of stacking at each stage to fabricate MCIF. (Image by SIOM)

Fig. 2. (a) Distribution of core diameters. (b)-(d) Coupling efficiency between core1&core3, core1&core2, core2&core3 at 650 nm. (e)-(g) at 850 nm (h)-(j) at 1000 nm. The dashed lines are calculated coupling efficiencies between cores of the designed diameters. (Image by SIOM)

Fig.3. The imaging of UASF targe by our MCIF under different bending radii at 650 nm wavelength. (Image by SIOM)

Article website:
https://doi.org/10.1016/j.optlastec.2022.108650