Friday, July 8, 2011

Five Minute Fiber Expert- The Fiber Optic Gyroscope (FOG)

Five Minute Fiber Expert 4 - The Fiber Optic Gyroscope (FOG)

Last time you learned about our BIG Product, Bow-Tie PM Fiber – this month, it’s the turn of the BIG Application. So let’s answer five simple questions:

1. What is a gyroscope?

2. What is a fiber optic gyroscope?

3. What makes a fiber optic gyroscope better?

4. Why does a FOG need Bow-Tie PM fiber?

5. What are the key PM fiber design elements?

Put simply, a gyroscope is a device that measures rotation. So, by using a gyroscope, you can find out where something is pointing (e.g. an aircraft) or how level it is (e.g. a hovering helicopter, a high-speed train carriage or even a pair of binoculars). This is why gyros are used to help navigate ships, aircraft and even some land vehicles and in systems used for automatically stabilizing things.

To be effective, you need one gyro for each degree of freedom (or ‘axis’) in which the ‘platform’ can move. Aircraft, for example, can move in three dimensions – so need three gyros to cover roll, pitch and yaw.

Traditional gyroscopes have been around for more than 100 years and work on the ‘spinning mass’ principle. Those of you who had a gyro top as a child, or have played with one of those wrist-strengthening balls will recall that when you spin the rotor, the gyro gets a mind of its own and wants to remain upright? Well it’s the force that the gyro exerts trying to right itself (aka ‘gyro torque’) that can be used to determine how far you have tried to rotate it.

A FOG achieves the same result, but using polarized light and something called the Sagnac Effect. The Sagnac Effect states that if light travels simultaneously in both directions around an enclosed optical system and the optical system experiences a rotation, the light will undergo a Doppler-Shift (remember how police sirens change pitch as the car speeds past you?…same thing) with the result that the two beams will recombine out-of phase, creating interference. If you analyze this interference, you can find out the degree and the rate of rotation. In essence, a simple FOG looks a bit like this:

The true benefit of FOG over a traditional, spinning-mass gyro is that it has no moving parts – no moving parts means nothing to wear out and nothing to service. As a result, FOGs are tougher, more reliable and demand far less maintenance. In fact one Fibercore customer found that the military could use one of their systems for an average 30 times longer before repair, simply by switching from conventional gyros to FOG. Another advantage of FOG is that it is ready to work immediately, whereas a spinning-mass gyro can take up to 30 seconds to spin-up and stabilize. 30 seconds might not seem that much – but those of you old enough to remember the Cold War, will also remember that we would only have had three minutes to wait from detection to destruction. Right up until the early 1980s – 30 seconds was a long time!

The optical fiber in a FOG enables a very long optical path length to be confined into a small volume and so magnify the small phase shift caused by the Sagnac Effect – and the longer the path length, the more accurate the FOG. Satellite manufacturers often ask for long lengths of continuous fiber, sometimes up to 5,200 m lengths of HB1500G variants – this is because the fiber is used in the very accurate FOGs used in satellites launched by the European Space Agency (ESA) that make sure that the solar cells are always pointing at the Sun. And if those solar cells stop pointing at the Sun, the satellite dies – so I guess we play a pretty important part in ensuring the success of ESA missions!

The fiber used in FOGs needs to preserve polarization because, in order to generate stable interference, two light waves have to have the same orientation – if they crossed at right angles, they wouldn’t even know the other one was there! Typically, people want to get the longest optical path length into the smallest possible space and this leads to small diameter coils with multiple layers – demanding lots of birefringence (short beat-lengths) to make sure that the micro-bending created within these layers does not counteract the stress inside the fiber (see 5-Minute Expert #3), high numerical apertures to ensure that the fiber continues to guide strongly in these small coils (see 5-Minute Expert #1) and reduced fiber diameter, to improve lifetime and save space (see 5-Minute Expert #1). All of which go a long way to explaining our current development direction of ultra low-profile, ultra-high birefringence Bow Tie PM Fiber.

Fibercore’s product range can be found at

Thursday, July 7, 2011

LEOK-2 Holography and Interferometry Kit

Holography and Interferometry Kit


1-5 fundamental experiments

2-Detailed instruction manual

3-Easy alignment and setup

4-Affordable price


The Holography and Interferometer Kit is developed for general physics education at universities and colleges. It provides a complete set of optical and mechanical compone

nts as well as light sources. Through selecting and assembling corresponding components into setups, students can enhance their experimental skills and problem solving ability. The instruction manual contains comprehensive materials including experiment setups, principles, procedures and required parts with photos. This kit will help students understand the fundamentals and applications of holography and interferometry.

Using this experiment kit, the following 5 experimental examples can be conducted:

1-Recording and reconstructing holograms

2-Making holographic gratings

3-Constructing a Michelson interferometer and measuring the refractive index of air

4-Constructing a Sagnac interferometer

5-Constructing a Mach-Zehnder interferometer

For more information, please click:

Five Minute Expert: ‘Bow Tie’ Polarization Maintaining Fiber

‘Bow Tie’ Polarization Maintaining Fiber

Well, here it is, ‘The Big One’. So what makes it different from standard, telecommunications fibers, and how does it work?

As you can see, it got its name because it was invented in 1982, so long ago that Fabricators wore bow-ties – because an ordinary tie could too easily have become wrapped around the lathe ...…OK, so I made this bit up, but at least you were listening!

The distinctive cross-section of a bow-tie fiber is created by the two segments of boron-doped glass that flank the core (you may hear these segments being called SAPs or stress-applying parts). As the fiber cools during the drawing process, the boron makes the S

APs contract more than the rest of the fiber, placing the core in tension. This tension stretches the glass structure along the axis running parallel to the stress and compresses it along the axis running perpendicular to it and, in doing so, changes its optical properties. Light moves less easily through the compressed, densified structure, causing it to travel more slowly – and conversely, more easily and more quickly through the stretched structure. In this way, the fast and slow axes are created – the fast running perpendicular and the slow, parallel to the SAPs. This is called birefringence.

A lot of people (including some of our customers) think that the elliptical shape of the core is caused by stress – it isn’t. The core shape is formed in the preform, during the collapse phase of the fabrication process, when the glass is molten and cannot support stress – the birefringence can only start to happen after the glass has solidified.

Birefringence can be a useful thing to have in a fiber because it causes light waves to travel at different speeds, depending on their orientation relative to the SAPs – so if your optical source is polarized, i.e. if all of the light waves it generates have the same orientation, and you line them up to the fast or to the slow axis, then the polarization state of the source will be maintained – and you have a polarization maintaining or ‘PM’ fiber.

Fibercore’s product range can be found at

Wednesday, July 6, 2011

Sponsor- Fasting and Sustainable Health Conference 2010

An Invitation

The first ever Fasting and Sustainable Health Conference 2010 will explore the sciences of fasting of different religions, in an effort to understand the relationship between fasting and wellness.The conference will delve into the effect of fasting on daily life ; the effect of fasting on medicine including military medicine as well as the scientific aspect of the relationship between fasting and exercise.A number of prominent speakers from academic institutions and various religions in Malaysia will be invited to share their knowledge on the aspect of fasting covering the discipline of wellness, medicine, defense and sports. This conference will be held at a prestigious hotel, Eastin Hotel, on the Island of Penang (Pulau Pinang Pulau Mutiara), which is famous for its culture, food, tourism and its pristine beaches.

Scientific Programme

Fasting and Sustainable Health Conference 2010 will cover topics which will be of interest to healthcare professionals, researchers, academicians as well as members of the public who are interested in understanding more deeply the rituals, reasons and effects of fasting. Apart from the lectures and forums, researchers are invited to present their findings on various aspects of fasting in oral and poster presentations.


  1. To know the science of fasting of the different religions.
  2. To know the relationship between fasting and wellness.
  3. To know the effect of fasting on fitness and physical exercise.
  4. To know scientific views about the role of fasting in medicine, military medicine and its effect on daily life.

Titles of Invited Presentation:

  1. Science of Fasting: Aspects From Islamic Perspective.
  2. Science of Fasting: Aspects From Christianity Perspective.
  3. Science of Fasting: Aspects From Buddhism Perspective.
  4. Science of Fasting: Aspects From Hinduism Perspective.
  5. Science of fasting: Aspect from the Baha'i Community.
  6. Ramadan Fasting: Health benefits & risks (in diabetics).
  7. Science of fasting: Aspect from Defense Medicine.
  8. Fasting and Sports Performance
For more information, click here;