The propagation of electromagnetic waves in the optical fiber belongs to the medium circular waveguide. When the light is totally reflected at the interface of the medium, the electromagnetic wave is confined in the medium, which is called guided wave or guided mode. For a given guided wave and working wavelength, there are many incident situations that satisfy the condition of total reflection, which are called different modes of the guided wave. According to the transmission mode, it is divided into multimode fiber and single mode fiber. Multimode fibers can transmit several modes, while single-mode fibers can only transmit one mode for a given operating wavelength.

Single-mode fiber optic cable In fiber optic communications, a single-mode fiber optic cable is a fiber optic cable designed to carry a single beam (mode). It is mainly composed of core, cladding and coating layer.

Single-mode fiber (Single-Mode Fiber, SMF) or sm. It is mainly composed of core, cladding and coating layer; the core is made of highly transparent material; the refractive index of the cladding is slightly smaller than that of the core, resulting in an optical waveguide effect, so that most of the electromagnetic field is absorbed Bound in the fiber core for transmission; the function of the coating layer is to protect the fiber from water vapor erosion and mechanical abrasion, and at the same time increase the flexibility of the fiber. Outside the coating layer, a plastic jacket is often added.

Outdoor Single Mode Optical Cable

Single-mode optical cable and multi-mode optical fiber can adopt step refractive index distribution, and can also adopt gradient refractive index distribution; single-mode optical fiber mostly adopts step refractive index distribution. Therefore, the silica fiber can also generally adopt three types: multi-mode step-index fiber, multi-mode graded-index fiber and single-mode step-index fiber. The propagation of electromagnetic waves such as light in the optical fiber belongs to the medium circular waveguide. When the light is totally reflected at the interface of the medium, the electromagnetic wave is confined in the medium, which is called guided wave or guided mode. For a given guided wave and working wavelength, there are many incident situations that satisfy the condition of total reflection, which are called different modes of the guided wave. According to the transmission mode, it is divided into multimode fiber and single mode fiber. Multimode fibers can transmit several modes, while single-mode fibers can only transmit one mode for a given operating wavelength.

The meaning of the cut-off wavelength λc is the minimum working light wavelength that enables the fiber to achieve single-mode transmission. That is to say, although other conditions are satisfied, if the light wavelength is not greater than the cut-off wavelength of the single-mode fiber, it is still impossible to achieve single-mode transmission.

According to the number of transmission modes in the fiber, the fiber can be divided into multi-mode fiber and single-mode fiber. at a certain operating wavelength. Multimode fiber is a dielectric waveguide capable of transmitting many modes, while singlemode fiber only transmits the fundamental mode.