What is hollow core fiber? Hollow-core fiber (HCF) uses air as the transmission medium, replacing the traditional optical fiber that uses "glass core" as the transmission medium. With ultra-low latency, ultra-low nonlinearity, potential ultra-low loss and wider passband bandwidth, hollow-core fiber can help OTN systems achieve greater transmission capacity, longer transmission distance, and smaller transmission time delay.

1.Hollow core optical fiber light guide principle

Different from the total reflection principle of conventional optical fiber waveguide light guides, the core of hollow-core optical fibers is air, and light guidance depends entirely on the restriction of light by the cladding. For example, highly reflective silver can be used to constrain the reflection of light so that it can only be transmitted in the air core. This technology was first proposed in the 1960s. It coats the inner wall of a glass capillary with a reflective film and then transmits mid-infrared light in the middle. However, because the hole is relatively large, it is easier to coat, but the larger the hole, the more modes of transmission will occur. In this structure, it is more difficult to achieve long-distance single-mode transmission.

2.Hollow core fiber VS glass core fiber?

Compared with the currently widely used glass-core optical fiber, hollow-core optical fiber has significant advantages in the following aspects.

Low latency: Light is mainly transmitted in the core area close to air holes. The refractive index is lower than that of solid glass, and the transmission speed is faster. The latency drops from 5us/km to 3.46us/km. The transmission latency is compared with existing optical fibers. The system is reduced by 30%. It is very important for current and future delay-sensitive service transmission.

Ultra-low nonlinearity: The nonlinear effect of hollow core fiber is 3 to 4 orders of magnitude lower than that of conventional glass core fiber, which allows the input optical power to be greatly increased, thus increasing the transmission distance. Various equipment manufacturers in the industry, including ZTE, have started research on related optical systems based on this feature, such as 128QAM high-order modulation and high-power amplifier technology, which are expected to increase system capacity and transmission distance by at least 2 times.

Potential ultra-low loss: The current loss achieved by hollow-core optical fiber is 0.174dB/km, which is the same as the performance of the latest generation of existing glass-core optical fiber.At the same time, the theoretical minimum limit of the communication window of hollow-core optical fiber can be as low as 0.1dB/km, which is smaller than the theoretical limit of 0.14dB/km of ordinary glass-core optical fiber.

Ultra-wide operating frequency band: With the continuous optimization of hollow-core fiber structure design, it can provide an ultra-wide frequency band exceeding 1000nm, easily supporting O, S, E, C, L, U and other bands.

3.Howllow core fiber splicing.

Because of special structure of hollow core fiber. It's very hard to splice it. Shinho S-12PM fusion splicer could splice hollow core fiber at a very low loss. PM fusion splicer is a high precision alignment fusion splicer to splice specialty fibers like PM fiber,PCF and Hollow core fiber. Shinho S-12PM fusion splicer has good splice ER and loss.Help you deal with all kinds of specialty fibers.