21
Dec
Fibre optic cables
PAT Roberts

Optical filters and their uses in optical communications

With in-person festivities still under pressure this Christmas, many more of us will be keeping in touch with friends and family via digital communications.

Optical filters have a crucial role to play in enabling this, and will be the unsung heroes of long-distance get-togethers for many families over the holidays.

But what do those little sheets of glass and polymer actually do to make optical communications work the way we want?

How does optical communication work?

Fibre optic communication has taken over from copper cables as the way to transmit data at lightning-fast speeds, supporting the types of broadband speeds even residential customers have come to expect in the 21st century.

Pulses of light carry binary data along a thin strand of glass – light on for 1, light off for 0 – and this is received and decoded to turn the light beam back into computer data.

Optical fibres were originally developed to be used in endoscopy, allowing surgeons to look inside a patient’s body with only a very small incision, or by entering through an orifice.

Scientists soon realised that pulses of light could be transmitted along the fibre to carry data, at about 120,000 miles per second or roughly two thirds of the speed of light in a vacuum.

How do optical filters help?

Optical filters have an important role to play in supporting optical communications. At their most basic, they allow the signal light to be processed in some way, such as to restrict it to a specific frequency or band of frequencies.

More complex optical filters can process the signal in more complicated ways, enabling multiplexing of data.

The structure of a fibre optic is also carefully designed to prevent signal loss, by using a variety of refractive indices to ‘steer’ the signal light towards the centre of the fibre and reduce attenuation due to it reflecting from the walls of the cable.

Together, this gives developers close control over the signal transmitted, and can allow data to be transferred very quickly over long distances.

Bespoke optical filters for telecoms

Envin Scientific develop and supply bespoke optical filters for telecommunications applications, usually operating on laser diodes in the NIR 830, 1,310 and 1,550 nm wavelength regions.

Optical filters can modify the signal, divide it into multiple sources, and can also couple multiple fibres together using low-loss ball lenses to minimise attenuation at the connection point.

We are able to apply these techniques to other wavelength regions too – so if you have a custom fibre optic installation operating at a frequency not normally used in optical telecommunications, we can create bespoke optical filters to suit.

Our optical filters are hard and durable, and we can work to specifications such as flatness and parallelism as required. Finished products are tested using Perkin Elmer Lambda 900 & 983G Spectrophotometers to verify the filter’s characteristics.

To find out more or to make an enquiry about bespoke optical filters for your fibre-based communications installation, contact Envin Scientific today and a member of our team will be happy to help.