A three-core photonic crystal fiber (TCPCF) vector bending sensor for measuring spine curvature is proposed. Refractive index variations of the TCPCF due to the wavelength differences in the range of 1.25 to 1.85 μm are studied. We show a linear relation between refractive index and operating wavelength. The wavelength of 1.55 μm is chosen for simulation with high energy modules to compensate for bending loss. An asymmetrical fiber is designed to sense both the direction and magnitude of the curve. The asymmetrical geometry of fiber creates an asymmetrical refractive index profile that leads to shifts in light speed in different fiber sections. This geometry asymmetry, in turn, provides the information needed to calculate both variables. Bending effects on the TCPCF has been numerically studied by the finite element method. Data analysis shows that the proposed sensor is sensitive to bending with a sensitivity of 1.2199 pm.m. It also reveals high directional sensing.

.One of the modern ways to diagnose diseases is through exhale gas of patients, which is non-invasive and therefore desirable to doctors. The composition of exhaled breath contains valuable information for identifying hyperbilirubinemia disease. The accumulation of bilirubin and its lack of excretion causes jaundice, and the production of bilirubin has a direct relationship with exhaled carbon monoxide (CO). A CO diagnostic sensor based on a photonic crystal fiber (PCF) that can detect hyperbilirubinemia has been designed. This method can be used repeatedly to detect and treated jaundice in time. The PCF is designed as a hexagon. The holes in the cladding are circular and the holes in the core are circular and oval. Finite element method is used to do all the numerical simulations. COMSOL Multiphysics software was used to obtain the results. In this setup, CO absorption wavelength is 1.567  μm, and the relative sensitivity of 64.28% is reported with confinement loss of 3.81  ×  10  −  3  dB  /  m.

One of the ways to diagnose cancer in its early stages, which can lead to timely treatment, is to use Raman spectroscopy. The Raman spectrum of a material is created by the interaction of light with the material; it determines the exact characteristics and properties of the material, which can be used to distinguish cancerous cells from healthy ones. However, the intensity of this spectrum is weak, and the optical fibers used in these devices must have very little loss and thus have low sensitivity to bending. This paper proposes a circular photonic crystal fiber with a structure in which the losses in different bending radii are significantly reduced. The modified state of the fiber at the wavelength of 1.55 μm supports the transmission of 10 modes propagated in the core. The loss for the fundamental mode at this wavelength and bending radius of 2 mm equals 3.82 × 10 −16 dB∕m, which is considered a low value. As the bending radius decreases further, low-order modes diminish, which are more sensitive to bending than high-order modes. However, their losses are lower than in high-order modes. The critical bending radius for this fiber, with the loss reaching 0.1 dB∕m, is equal to 0.096 mm. This low critical bending radius shows the low sensitivity of the proposed fiber to bending. The fiber was examined in different bending radii and wavelengths, and the parameters of this structure were presented for the lowest bending losses, which can be used in Raman spectrometers as spectrum collecting fibers and improve cancer diagnosis devices with Raman spectrum.