Near-infrared filter for optical communication

Abstract

The invention discloses a near-infrared filter for optical communication. A substrate of the filter is made of transparent or colored glass such as optical glass and jewel. The two sides of the substrate are respectively plated with a band-pass filter film and an antireflective film. Therefore, 760-900nm light can be transmitted efficiently, and 400-760nm and 900-1100nm light can be cut off. Signal light within near-infrared bands is transmitted efficiently, and stray light in other bands (visible light especially) is cut off, thus obtaining high signal-to-noise ratio. The spectral curve of the filter film system has high pass-band transmittance, approximately rectangular pass-band shape, small pass-band ripple, high out-of-band cut-off depth and wide cut-off range. The location requirement of the film system is reduced, and the rate of finished products is improved. By adopting the near-infrared filter for optical communication prepared by the use of the film system structure and the preparation method, the influence of stray light in other bands can be effectively suppressed while as much signal light as possible can be acquired, and the signal-to-noise ratio is significantly improved.

Description

technical field [0001] The invention relates to an optical filter film, in particular to a near-infrared filter used in optical communication, capable of efficiently transmitting near-infrared signals for communication and simultaneously suppressing out-of-band background light. Background technique [0002] In visible light communication (visible light communication, VLC), it is generally necessary to have both downlink and upload functions at the same time; therefore, in addition to the downlink signal of the white light LED that integrates lighting and communication, a near signal that is different from the white light band generated by the downlink LED is also required. Infrared signals are used as upload signals. The wavelength range of infrared LEDs commonly used to generate near-infrared signals is 760nm to 900nm. It is worth noting that silicon detectors typically respond to a wide range of signals (e.g. figure 1 ), the response wavelength ranges from about 400 to ...

AI Technical Summary

Problems solved by technology

In general, in order to ensure the above characteristics, both the high-pass filter film and the low-pass filter film need to be realized with a complex film system with more than 50 layers, which greatly increases the number of experiments and the difficulty of preparation.

[0004] In addition, in order to ensure that as much signal light is transmitted as possible while suppressing as much out-of-band stray light as possible, the double-film system needs to be positioned accurately, otherwise it may cause too much signal sacrifice or too much noise; and the high-pass filter The transmission area between the membrane and the low-pass filter interacts with each other, and very large passband ripples are prone to occur

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