Photonic crystal fibers are a kind of fiber optics that present a diversity of new and improved features beyond what conventional optical fibers can offer. Due to their unique geometric structure, photonic crystal fibers present special properties and capabilities that lead to an outstanding potential for sensing applications. A review of photonic crystal fiber sensors is presented. Two different groups of sensors are detailed separately: physical and biochemical sensors, based on the sensor measured parameter. Several sensors have been reported until the date, and more are expected to be developed due to the remarkable characteristics such fibers can offer.

A sensing system for micro-displacement measurement based in a suspended-core fiber Sagnac interferometer is presented. The suspended-core fiber characterization was made through the use of an optical backscatter reflectometer, screening its multimodal and birefringent behavior. Its sensitivity to displacement measurements is shown to be due only to birefringence, being that core-cladding mode coupling is negligible. High precision ($\sim 0.45\mathrm{\mu m}$) was obtained using three different measurement instruments, showing an extremely high stability and high insensitivity to temperature, demonstrating that the sensing system has the ability for low cost applications.

In the present work, a simple temperature fiber laser sensor configuration is proposed. The temperature fiber laser sensor is based in the combination of a Fabry-Perót hybrid cavity and a random mirror. The Fabry-Perót hybrid cavity is fabricated by splicing a single mode fiber with a small piece of suspended-core fiber. The random mirror is created by multiple Rayleigh scattering events running along the dispersion compensation fiber, as a direct consequence of Raman gain in this fiber. In the proposed configuration, the Fabry-Perót cavity presents simultaneously a double function: laser reflective mirror and temperature sensing cavity. The proposed temperature fiber laser sensor presents maximum output power of ~4 mW in a 15nm wavelength range while providing a temperature sensibility of ~6 pm/^°C, in a 200^°C temperature range.

Different multiwavelength Raman fiber lasers based on a hybrid cavity setup are proposed. The lasing schemes are based in highly birefringent photonic crystal fiber loop mirrors combined with random cavities. The Hi-Bi PCF loop mirrors are characterized by an interferometric output; whereas the random mirrors are created by cooperative Rayleigh scattering due to Raman gain. This configuration allows suppression of Rayleigh associated noise growth, while taking advantage of it as an active part of the laser cavity, enhancing the achievable gain. The proposed fiber lasers present stable operation at room temperature although different output maxima and shapes depending on the fiber loop mirror/random mirror combination.

In the present work, a multiwavelength fiber laser based in the combination of a double-random mirror and a suspended-core Sagnac interferometer is presented. The double-random mirror acts by itself as a random laser, presenting a 30dB SNR, as result of multiple Rayleigh scattering events produced in the dispersion compensating fibers by the Raman amplification. The suspended-core fiber Sagnac interferometer provides the multi peak channeled spectrum, which can be tuned by changing the length of the fiber. The result of this combination is a stable multiwavelength peak laser with a minimum of ~25dB SNR, which is highly sensitive to polarization induced variations.