INTRODUCTION TO OPTICAL FIBERS FOR LIDAR

LIDAR is a technology that is getting increasing attention in today’s world, having sparked a lot of interest in the general media outside of the scientific community in recent years. LIDAR stands for Light Detection And Ranging. In its simplest form, it’s a technology that enables the detection of objects at a distance using light and that can be understood as being a radar that uses laser light instead of radio waves.

General Principle of Time-of-Flight LIDAR

The most used LIDAR technique is what is called “Time-of-Flight” LIDAR. The method is conceptually simple: a laser beam is sent forward, and the laser light is reflected off an object back towards a detector. Next, we measure the time between the laser beam being sent and its reflection being received. Since we know the speed of light, the distance to the object can be calculated. If we then want to create a full 3D image of what’s in front of us, the previous process will generate one “pixel” of our image. If the laser source is then able to perform a scan by moving vertically and horizontally, we can send a series of laser pulses during that scan to map an image point-by-point.

Different types of laser sources can be used to build a LIDAR system, at different wavelengths, as long as the power is high enough so that the returning power can be detected, since most objects will only reflect a small fraction of the original laser beam. Optical fibers can be used to build LIDAR laser sources at wavelengths around 1.5 µm. Read on for the advantages of this technology.

Applications of LIDAR Technology

The first applications of LIDAR technology were for direct ranging applications to generate 3D mapping of objects, buildings, landscapes and more. Wind and environmental sensing are also very important applications of LIDAR, where we can use the backscattered light from the atmosphere to measure wind speeds, profile cloud shapes or identify the presence of certain gases.

In recent years, it’s the use of LIDAR in automated vehicle systems that has brought the most attention to this technology, feeding the dream of putting self-driving cars on the road. The main advantage of adding LIDAR systems to a series of sensors on a vehicle is to add additional information about the environment where a camera would not be able to see (in the dark, under certain weather conditions) or where a standard radar would not have the required resolution.

Even without considering the full self-driving capacities of a vehicle, LIDAR technology can be used in driving assistance systems for both practicality and safety. These systems can give very accurate range information about nearby vehicles and obstacles and help input more data into automated braking systems even when there is a driver behind the wheel.

There are also many other emerging applications in industrial environments like mines, ports and warehouses where automated systems using LIDAR can improve efficiency and reduce accidents. Smart city and road infrastructure of the future could also use LIDAR to map public roads in real time, adding another level of inter-connection and safety.

Where Do Optical Fibers Fit In?

One family of LIDAR technologies is in the 1.5 µm wavelength range, and an efficient way of building a high-power laser amplifier at this wavelength is to use rare-earth doped optical fibers, particularly erbium doped or erbium/ytterbium co-doped fibers. Coractive is a leader in the manufacturing of these types of fibers, so take a look at our portfolio of fibers for LIDAR.

Fiber amplifiers are great to use in such systems since they are robust, able to scale to high power easily and can use components originally designed for telecommunication systems that have proven their worth for decades.

Using a 1.5 µm wavelength in a LIDAR system instead of other technologies such as 1 µm lasers (generally using light from laser diodes from 915 nm to 980 nm) has certain advantages:

The 1.5 µm wavelength region is significantly more “Eye safe”, meaning that more power can be used before reaching any limit in terms of damage to human eyes in the case of direct illumination by the laser. This is because infrared light with a wavelength of 1400 nm or longer has more attenuation by the transparent parts of the eye before it reaches the retina.
This means the LIDAR system can use more power and consequently “see” at a longer range in a time-of-flight application. Since optical fiber amplifiers offer great power scalability at 1.5 µm, they are a good match for creating long range LIDAR.
It’s also a good wavelength to use to avoid some unwanted noise. The idea is to use a signal wavelength that is very well isolated from other possible illumination, such as sunlight.

It’s an exciting time in the world of LIDAR applications and if you’re interested in this field, contact Coractive’s experts to have a chat!

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