Understanding Single Mode Fiber and Cladding Materials

In summary: This is actually possible, and is referred to as an "integral" configuration. In this configuration, the light will still follow the bend in the fibre, but the beam will be "integrated" across the entire length of the fiber. This is useful for transmitting large amounts of light over long distances without having to break the beam up into smaller segments.
  • #1
dervast
133
1
Hi i have some questions concerning optical fibers.. I want to know how the single mode fiber works.. I know that the light in sinle mode fiber travels across the middle of the fiber.. I can't understand why if we bend a little the fiber why the light don't hit the walls of the fiber?
Thx a lot
 
Science news on Phys.org
  • #2
The beam, will and does hit the sides. Optical fibers have a core and a cladding material which have Indexes of refraction such that when the beam hits the wall it will be totally reflected. A key word here is the Brewster Angle so some research on that. All optical fibers have a minimum bend radius, if you attempt to make a corner with a bend less then the minimum bend radius you will have high loss. As long as you stay within the specified bend radius you will maintain good power levels.
 
  • #3
Integral, I think you mean the critical angle, Brewster angle has to do with the polarisation of reflected light.

Dervast, the conceptual picture of a single ray traveling down the centre of the fibre is an imperfect analogy as it does not consider the field nature of light. Ray analysis is really only applicable for fibres with many modes (about 8 or greater).

Claude.
 
  • #4
Thanks for the correction Claude, this what happens when you dredge up 30yr old terms from your memory.:blushing:
 
  • #5
Thx a lot but waht do u mean by "the conceptual picture of a single ray traveling down the centre of the fibre is an imperfect analogy as it does not consider the field nature of light."

Why the signle ray ignores the nature of light?? I can't understand that... When i send a ray of light in a specific direction the light will continue moving in that direction.. One guy told me as a reply to this that the signle ray is too small as we are concerning the size of earth... When we move on the surface we can't understand the curved Earth because we are many times smaller than the Earth .. But still i don't think that the example is good enough for that... Because the single optical ray travels to the "air" and is not using trhe ground for that... Do u have to suggest me sth now?
Thx a lot
 
  • #6
Thx a lot guys but i want to learn and if u have sometime please try to reply me... thanks a lot really
 
  • #7
I'm certainly not overly knowledgeable about physics (I'm a freshman engineer), but I do remember seeing something about fiber optics in a physics book at some point in time. If you're asking why the light doesn't just leave the fiber optic as it turns a corner here, I think the outer material has a very different refractive index, so it bends the light correctly to make the light follow the bend. If the radius is to low, it will exit the wall (can it be too high as well?). I at least some of this is correct, and answers your question.
 
  • #8
dervast said:
Thx a lot but waht do u mean by "the conceptual picture of a single ray traveling down the centre of the fibre is an imperfect analogy as it does not consider the field nature of light."

Why the signle ray ignores the nature of light?? I can't understand that... When i send a ray of light in a specific direction the light will continue moving in that direction.. One guy told me as a reply to this that the signle ray is too small as we are concerning the size of earth... When we move on the surface we can't understand the curved Earth because we are many times smaller than the Earth .. But still i don't think that the example is good enough for that... Because the single optical ray travels to the "air" and is not using trhe ground for that... Do u have to suggest me sth now?
Thx a lot

Light is an electromagnetic field, so in order to obtain a complete description of light in an optic fibre, you need to obtain a description of the E and B fields in the fibre, which is done by solving Maxwell's equations. The ray analogy only considers the direction of propagation of the light.

For example, the shape of the guided mode in a single-mode fibre is a Bessel function, which is well approximated by a 2D Gaussian curve (this is easily verified through experiment). This can only be derived using Maxwell's equations, ray analysis alone cannot give this result.

P.S. I would disregard what this 'one guy' said, I don't think he really understood your question to be perfectly honest.

Claude.
 
  • #9
we know that the cladding material is of lower refractive index than the inner core's refractive index.but what if instead of outer cladding glass material, air is used(which too has a lower refractive index)?would it also not cause TIR inside the core.
 

1. What are optical fibers?

Optical fibers are thin, transparent strands of glass or plastic that are used to transmit light signals over long distances. They are an essential component of modern telecommunication systems and are also used in medical and industrial applications.

2. How do optical fibers work?

Optical fibers work by using the principle of total internal reflection. Light is introduced into one end of the fiber, and it travels through the core of the fiber, bouncing off the walls of the core due to the difference in refractive index between the core and the cladding. This allows the light to travel through the fiber without significant loss of signal.

3. What are the advantages of using optical fibers?

Optical fibers offer several advantages over traditional copper wires. They can transmit signals over longer distances without the need for amplification, have a higher bandwidth, and are less susceptible to interference. They are also smaller and lighter, making them easier to install and maintain.

4. What are the different types of optical fibers?

There are several types of optical fibers, including single-mode fibers, which are used for long-distance communication, and multimode fibers, which are used for shorter distances. There are also specialty fibers, such as polarization-maintaining fibers and dispersion-shifted fibers, designed for specific applications.

5. What are some common uses for optical fibers?

Optical fibers are primarily used for communication purposes, such as in telephone, internet, and cable TV networks. They are also used in medical imaging and sensing equipment, such as endoscopes and laser sensors. In industrial settings, optical fibers are used for inspecting and monitoring equipment in hard-to-reach places.

Similar threads

I Light coupling in fiber optic cables
    • Optics
Replies
22
Views
2K
What Causes Molecules to Aggregate Over a Fiber in Optical Trapping?
    • Optics
Replies
2
Views
825
Connect: Coupling Light from 2 LEDs into a Single Fiber
    • Optics
Replies
2
Views
2K
What's the mode of light in single-mode fiber?
    • Optics
Replies
6
Views
17K
Polarization of elliptical fiber modes
    • Optics
Replies
2
Views
957
Evaluate the outgoing radiation from an optical fiber on a surface
    • Optics
Replies
1
Views
1K
B Is this material is good for fiber optics and who would buy it?
    • Optics
Replies
2
Views
998
How can light propagate through Hollow optical fiber.
    • Optics
Replies
7
Views
2K
Optic Fiber Project Ideas for Amateur Physics Student
    • Optics
Replies
2
Views
8K
How does Total Internal Reflection in a mm/sm fiber work?
    • Optics
Replies
3
Views
1K

Hot Threads

Recent Insights

Back
Top