We propose and demonstrate a sensing system with fiber Bragg grating (FBG) sensors designed as Discrete Prolate Spheroidal Sequences (DPSS). In this way, we can encode all of the sensing devices in the network making sure that each sensor is completely distinguishable from each other even under overlapping conditions. Since these devices are complex structures involving unique magnitude and phase response, the demodulation method should be able to recover the associated magnitude and phase response in order to identify each device in the sensing network. To do so, we use a Single Side Band (SSB) modulated optical source sweeping over the operational wavelength range of the sensors, the reflected signal from the sensors is sent to a Vector Network Analyzer (VNA) in which it is obtained the magnitude and phase ratio of the network in the microwave domain. Experimental demonstration has been carried out including the manufacturing of DPSS structures. Feasibility of the interrogation technique for devices involving magnitude and phase distinction has been validated, not only to identify encoded sensors in a measurement network but also to allow overlapping between them, which allow to increase the number of sensors allocated in the sensing network.

In this paper, an encoding strategy is used to design specialized fiber Bragg grating (FBG) sensors. The encoding of each sensor requires two binary codewords to define the amplitude and phase patterns of each sensor. The combined pattern (amplitude and phase) makes each sensor unique and therefore two or more sensors can be identified under spectral overlapping. In this way, we add another dimension to the multiplexing of FBG sensors, obtaining an increase factor ‘n’ to enhance the number of sensors that the system can handle. A proof-of-concept scenario with three sensors was performed, including the manufacturing of the encoded sensors. Furthermore, an interrogation setup to detect the sensors central wavelength was proposed and its working principle was theoretically developed. Results show that total identification of the central wavelength is performed under spectral overlapping between the manufactured sensors, achieving a three-time improvement of the system capacity. Finally, the error due to overlapping between the sensors was assessed obtaining approximately 3 pm, which makes the approach suitable for use in real measurement systems.

In this paper the design and initial development of a Fiber Bragg Grating (FBG) sensor interrogation system are presented. It uses an edge filter, among other optical components, and measures the wavelength signals with a microcontroller. The system was designed for the 1550 nanometers band with an acquisition rate of 2.5 kHz. The performance of the interrogator was tested obtaining a stable voltage ratio when changing the input signal and a linear performance of this voltage ratio when a temperature of 20-70° C is induced into a FBG sensor connected to the system. These results demonstrate the feasibility of specific, low-cost interrogation systems with high acquisition rates.

In this letter, a spectral encoding of fiber Bragg grating (FBG) sensors is proposed in order to solve their wavelength under overlapping conditions. Our technique uses optical orthogonal codes (OOCs) to define the spectral shape of the FBG sensors. In this way, we design encoded FBG sensors composed of more than one reflection band; the spectral location of the reflection bands is determined by the OOC, providing each encoded FBG sensor with a unique spectral signature. The demodulation technique for the proposed sensors makes use of their orthogonal nature: it obtains the wavelength position for each sensor by obtaining the autocorrelation product between the reflection spectrum and each sensor's spectral code. These FBG sensors have been manufactured and experimentally validated. The results demonstrate the overlap-proof nature of the encoded sensors. Furthermore, the very simple demodulation technique provides highly accurate wavelength detection and can be implemented in real-time detection systems.

This paper presents a temperature study of cellular spheroids of the line MCF-07 under a hyperthermia (HT) treatment. A 3D printed culture plate embedded with optical fiber Bragg grating (FBG) sensors was designed to perform real-time temperature measurements of the spheroids. The proposed culture plate preserves the fiber sensors' integrity and functionality while remaining immune to the high electromagnetic interference scenario. A custom microwave applicator was designed to eliminate direct contact between the heating element and the samples, while considering the culture plate material's permittivity to ensure efficient heating. The heating setup maintains the samples' temperature within the HT range, which is crucial for predicting treatment outcomes. The sensors embedded in the designed culture plate achieved an accuracy within 0.31 ${}^\mathrm{C}$ . Initial observations of the temperature effects on spheroids are discussed, highlighting the potential of this approach to understand how temperature variations within the HT range affect cell cultures.