I. Technical Principles and Characteristics

Fiber Bragg grating is an optical device that forms a periodic refractive index modulation structure within the fiber core through ultraviolet laser. Its core working principle is based on the Bragg reflection condition: when a broadband optical signal passes through the FBG, specific wavelengths of light (Bragg wavelengths) are reflected, while the rest of the wavelengths are transmitted. The Bragg wavelength drifts with changes in the external environment (such as strain, temperature, etc.), and this characteristic forms the basis for the application of FBG in sensing and communication.

FBG features multiple outstanding characteristics: high wavelength selectivity (narrowband reflection), low insertion loss, all-fiber structure, anti-electromagnetic interference, corrosion resistance, etc. These characteristics make it particularly suitable for long-term stable operation in complex environments.

Ⅱ. Applications in the Field of Optical Communication

In optical communication systems, FBG mainly performs the functions of wavelength selection and regulation:

1.Wavelength division multiplexer/demultiplexer

FBG can be used as a narrowband mirror to achieve the separation and combination of specific channels in dense wavelength division multiplexing (DWDM) systems. The cascading use of multiple FBGS with different cycles can form compact wavelength division multiplexing devices, significantly enhancing the capacity of optical fiber communication.

2. Dispersion compensation devices

By taking advantage of the wavelength-dependent group delay characteristics of chirped fiber Bragg grating (CFBG), the dispersion effect in optical fiber transmission can be compensated and the signal quality of high-speed communication systems can be improved. This scheme is more compact and economical than the traditional dispersion compensation optical fiber.

3. The wavelength of the laser is stable

Integrating the FBG as an external cavity reflector into the semiconductor laser can achieve precise locking of the output wavelength and improve the wavelength stability and side-mode rejection ratio of the laser.

4. Optical Division Multiplexing (OADM)

In metropolitan area networks and access networks, FBG, in combination with devices such as circulators, can form flexible optical distribution multiplexing nodes to achieve uplink and downlink functions of specific wavelengths.

Ⅲ. Applications in the Field of Optical Sensing

The application of FBG in the field of sensing is more diverse, mainly utilizing its wavelength modulation characteristics:

1. Physical quantity sensing

① Strain measurement: By monitoring the Bragg wavelength drift, high-precision strain detection can be achieved, with a sensitivity of 1.2pm/με

② Temperature sensing: The temperature sensitivity is approximately 10pm/℃, suitable for distributed temperature field monitoring

③ Pressure/vibration measurement: Through a special packaging design, dynamic pressure changes can be detected

2. Structural health monitoring

In fields such as aerospace and civil engineering, FBG sensor networks can monitor parameters such as strain and vibration of structures in real time. For example, deformation monitoring of aircraft wings, load distribution monitoring of Bridges, etc.

3. Biomedical sensing

Miniaturized FBG can be used in medical applications such as in vivo pressure monitoring (such as intracranial pressure) and temperature detection. Its biocompatibility and electromagnetic safety are significant advantages.

4. Special environment monitoring

The high-temperature resistance and radiation resistance of FBG make it suitable for parameter monitoring in harsh environments such as nuclear power plants and oil and gas pipelines.