What do lasers and optical fibres have in common?

February 12, 2018

 

 

Reading time: 6 min | Difficulty: High | Sources: 8 out of 12 are open access

 

 

The answer is “light!” But wait, don’t stop reading just yet. We have more questions for you. What’s the science that studies light and its applications? What is light composed of? What does the word laser stand for? What is an optical fibre? And - Why should I care about this?

 

Having a chemical engineering background, it wasn’t until I started a project in physics that I became fascinated by the science of light. The project consisted of studying of an optical fibre sensor to monitor a winemaking process. Light was used to see the evolution of wine without taking a sample of wine or doing time-consuming laboratory analyses. This was very important because the process in analysis had a significant impact on the final product. The optical fibres used offered an easy, low cost solution that required non-skilled handling; thereby overcoming existing difficulties and improving analysis time. Since then, I have been very fascinated by the amazing possibilities that light offers, in particular, the amount of questions that light can solve, which is why I decided to go abroad and do a PhD in the field.

 

The transition between fields of study is not always easy. However, I learned by building upon previous knowledge and it was useful to have interdisciplinary experience. Here, I've answered to 5 key questions about the science of light.

 

What’s the scientific name for the science of light?

Photonics is the science of light. It is the technology of the generation, control and detection of light waves. It is also common to say Optics and Photonics. Some authors defend that in this expression the light’s dual nature is explicit: as a propagating wave and as a particle (photon). Optics and Photonics are specialised fields within physics and engineering.

 

What is light composed of?

Light waves are composed of photons, which are the particles of light. The colours that we see are only a small part of the entire light wave range, where each colour has a specific wavelength range. Photonics works with a wider range of wavelengths including the infrared and ultraviolet wavelengths. The entire electromagnetic spectrum englobes gamma rays, x-rays, ultraviolet, visible, infrared, microwaves and radio wavelengths.

 

What does laser stand for?

Laser is the acronym of Light Amplification by Stimulated Emission of Radiation. Laser light is a form of electromagnetic radiation and relates to the energy emission associated with the transition of an electron, from a higher to a lower energy level, within an atom. This happens when the atom absorbs a photon, thus becoming excited to a higher state. When the excited atom is stimulated by a photon it releases another photon as it transitions to a lower state, resulting in stimulated emission. The incident and emitted photons have the same characteristics and are in phase, resulting in coherent light (a group of photons act as a single unit), with the same direction, frequency and state of polarization.

 

What is optical fibre?

There are many types of optical fibres, a simple description being a cylindrical waveguide that consists of a central core in which the light is guided, surrounded by an outer cladding. They can be made in glass or polymeric material. There are also the optical fibre sensors that can be classified depending on the localization of the sensor (intrinsic or extrinsic), operating principle (intensity phase, frequency or polarization) and application (physical, chemical or biochemical).

 

Why should I care about this?

Because light is already being extensively used in our everyday lives and the number of applications is growing rapidly.

 

Laser light, for example, can be found in supermarkets scanners, CD players, laser pointers, medical devices, biosciences, electronics, high average power industrial applications (for cutting, welding or hardening), communications and astronomy. It has been used to study gases in the atmosphere of the Earth and in instruments that map the surfaces of planets.  

 

The optical fibre has revolutionised communications allowing for faster internet connections due to an enormous bandwidth when compared with the metallic cable systems. Other main advantages are small size, low weight, electrical isolation, immunity to interference and crosstalk, signal security, low transmission loss, ruggedness and flexibility, system reliability, ease of maintenance and potential low cost.

 

Finally, light is also being applied in precision sensing, imaging and metrology. Precision sensing is being performed increasingly with optically based measurements. Optical fibre sensors have been applied to the measurement and monitoring of strain, temperature, displacement, bending or torsion, vibration, acceleration, rotation, current/voltage and chemical detection. The advantages of optical fibre sensors over conventional electronic sensors are: immunity to electromagnetic interference, high sensitivity, compactness, light weight, inability to conduct a current, large bandwidth, robustness/resistance to harsh environments, and the possible use in-situ or distribution with remote sensing capability.

 

It’s amazing what we can do with light and its properties. Photonics is a technology with a “bright” future, so don’t be surprised if this word comes popping up more and more often.

 

 

 

 

 

About the author

Catarina Novo graduated in Chemical Engineering at University of Aveiro (Portugal) and research has been a passion ever since.

Living in Edinburgh since 2014, she is currently a Physics PhD researcher at Heriot-Watt University, working on microstructured optical fibre sensors. Catarina loves to get involved with science outreach and has been with Native Scientist since 2015.

She enjoys long walks on the beach, traveling, sharing a good meal with friends and family, and dancing.

 

 

 

 

 

 

Sources:

Open access

- What is Photonics (2015 International Year of Light)

- What are Optics and Photonics (OSA The Optical Society)

- Introduction to electromagnetic waves (Khan Academy)

- Principles of Laser Materials Processing (Wiley)

- Classification of fiber optical sensors (IJECCT)

- Lasers in Space (Proc. of SPIE)

- NASA Space Place (NASA)

- Optical Fiber Communications (Pearson)

Non-open access

- Optical fibre monitoring of Madeira wine estufagem process (Proc. of SPIE)

- Optics and Photonics (The National Academies Press)

- Fundamentals of Photonics (Wiley)

- Review of the present status of optical fiber sensors (Elsevier)

 

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