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

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

Outdoor single-mode fiber optic cable

Single-mode optical fiber multi-mode fiber can use step index distribution, but also can use graded index distribution; single-mode fiber mostly adopts step index distribution. Therefore, in general, the silica fiber can also adopt three types of multi-mode step-index fibers, multi-mode graded-index fibers and single-mode step-index fibers. The propagation of electromagnetic waves such as light in optical fibers 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 operating wavelength, there are multiple 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 multi-mode fiber and single-mode fiber. Multimode fiber can transmit several modes, while single mode fiber can only transmit one mode for a given operating wavelength.

The meaning of the cut-off wavelength λc is the Z-small working light wavelength that enables the optical fiber to realize single-mode transmission. That is to say, although other conditions are satisfied, if the wavelength of the light wave 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. under a certain working wavelength. Multimode fiber is a dielectric waveguide that can transmit many modes, while single-mode fiber transmits only the fundamental mode.