I am planning to concentrate the sunlight using the Fresnel lens into the fiber optic cable for my indoor experiments. But I am thinking that I will face the following problems:
1. The aperture of the Fresnel lens is very small. Can it hold and transmit all the light rays as the fiber optic cables have a particular angle of acceptance?
2. The magnitude of concentrated light is approximately 1000 x 1000 W/m2. Can the cable sustain the high temperature produced by the concentrated beam and transfer the sunlight from one place to the other place?
3. What are the losses which may occur in transporting the light along-with their magnitudes?
4. What is the maximum distance traveled by the concentrated light beam through the optical cable?
5. Where can I purchase the concentrated fiber optic cable from and how much it cost (approximately)?
I will be thankful to you if you answer any of the aforementioned questions.
Let`s make simple estimation: Angular diameter of sun is about 10 mrad. Maximum diameter of custom fiber bundle (available at the market) is ~2 cm. So maximum focal length of ideal concentrator is 2: 0.01 = 200 cm. Supposing maximum available NA (full acceptance angle) = 0.5, we obtain maximum diameter of concentrator 100 cm. So, available sun light power from one module "concentrator + fiber bundle" at the input is ~ 800 W. To get 1000x1000 W you need to use ~1250 modules (in the best case).
May be better to concentrate the light by spherical mirror instead Fresnel lens ?
Don`t worry about losses in fiber, main losses you will get before the input.
Standard fiber bundles have a length
Try using the fiber used in gooseneck bifurcated fiber optic illuminator which is available in the market. It has a large diameter with relatively large angle of acceptance. Also since it is used in conjunction with a high power electric bulb it may be able to withstand higher temperatures.
Dear Manoj Kumar Sharma ,
in order to avoid high temperature at the focus point please put an IR blocking filter in front of your lense.
Let`s make simple estimation: Angular diameter of sun is about 10 mrad. Maximum diameter of custom fiber bundle (available at the market) is ~2 cm. So maximum focal length of ideal concentrator is 2: 0.01 = 200 cm. Supposing maximum available NA (full acceptance angle) = 0.5, we obtain maximum diameter of concentrator 100 cm. So, available sun light power from one module "concentrator + fiber bundle" at the input is ~ 800 W. To get 1000x1000 W you need to use ~1250 modules (in the best case).
May be better to concentrate the light by spherical mirror instead Fresnel lens ?
Don`t worry about losses in fiber, main losses you will get before the input.
Standard fiber bundles have a length
The effect of plasma dispersion changes both real and imaginary refractive indices.
Although their number is different, there must be some influence of part of the loss in
the modulator's response to the RF signal. Are there any articles investigating this effect in high-
speed electro-optical modulators?
divide electro-optical modulation into external and direct action. The latter type of
modulation includes direct modulation of laser radiation to laser pump currents.
The modulation bandwidth can reach up to 10..20 GHz for various lasers. How
usually, this uses amplitude modulation or modulation
of the laser radiation intensity. The effects of the refractive index in lasers were studied. This
work is devoted to the modulation of quantum-dimensional laser diodes. The influence on
refractive index of the active medium of the pump current laser. As a constant component,
and the variable component.
Different types of electro-optical modulators are used for external modulation of laser radiation
. Mach-Zehnder modulators with a modulation bandwidth are widely used
up to 10...40ghz. But in such modulators, the refractive index of the material depends on the
modulating voltage. The temperature of the modulation region does not exceed significant
values.
Another class of external modulators includes absorption modulators, for example,
on semiconductor quantum-dimensional structures. Due to the high power density in
such modulators, the refractive index also depends
on the DC value and the average value of the variable component.
I was experimentally studying the transport of 1.06 µm laser radiation from a high-power neodymium laser using a quartz optical fiber.
We were able to transmit laser radiation at distances from 3 to 100 m.
It was possible to transmit power from 1 to 40 W in continuous mode.
Losses in the optical fiber itself were minimal and did not exceed 1...3 dB per 1000 m.
But large losses existed when entering laser radiation up to about 15..50% of the input power.
The losses significantly depended on the purity of the optical fiber input end surface.
When the surface of the optical fiber ends was poorly clean, an increase in temperature and "Gorenje" of the ends and the initial part of the fiber was observed at an input power of more than 10 W.
the radiation was usually entered using a standard lens (or a lens system).
We used optical fibers of different diameters with an optical core from 200 microns to 600 microns.
The best solution was to use fibers with optical core diameters of 350...600 microns.
If you will use Sunny study. Then the maximum of its spectrum falls on the green line or 0.55..0.57 microns. Therefore, you will face large losses in the optical fiber.
But the main problem you will have is the input problem.
I'm sorry the paragraph about modulators in the previous post referred to another post.. It should be read like this.
I was experimentally studying the transport of 1.06 µm laser radiation from a high-power neodymium laser using a quartz optical fiber.
We were able to transmit laser radiation at distances from 3 to 100 m.
It was possible to transmit power from 1 to 40 W in continuous mode.
Losses in the optical fiber itself were minimal and did not exceed 1...3 dB per 1000 m.
But large losses existed when entering laser radiation up to about 15..50% of the input power.
The losses significantly depended on the purity of the optical fiber input end surface.
When the surface of the optical fiber ends was poorly clean, an increase in temperature and "Gorenje" of the ends and the initial part of the fiber was observed at an input power of more than 10 W.
the radiation was usually entered using a standard lens (or a lens system).
We used optical fibers of different diameters with an optical core from 200 microns to 600 microns.
The best solution was to use fibers with optical core diameters of 350...600 microns.
If you will use Sunny study. Then the maximum of its spectrum falls on the green line or 0.55..0.57 microns. Therefore, you will face large losses in the optical fiber.
But the main problem you will have is the input problem.When using optical quartz optical fibers with a diameter of the light guide core of 300 microns..400 microns and an aperture of 0.2 ,we used a conventional lens with clear optics with a focal length of approximately 15...20 mm. The divergence of the laser radiation was 0.01 rad.
Look at the Fresnel lens in question and look up its focal length. That will allow you to calculate numerical aperture. Numerical aperture of a fiber is one of it's most important specifications, so when you pick a fiber, you can choose that. It will need to be >= the NA of the lens(es) used, or the main loss will be over filling the fiber.
That intensity is 1000X one standard sun, which, as you can imagine contains a lot of energy. Passing meaningful IR through the fiber isn't going to happen, so you will probably want to reject the spectral content above 1.9-2um or so with some kind of hot mirror.
There are quartz/quartz fibers that tolerate relatively high heat, (~300C) and Gold jacketed versions of these that can reportedly go to 700C. I have not used them personally, but they are advertised for that purpose. Making a bundle of these would be possible, but quite expensive
I can envision a possibility of capturing and transmitting visible-1.9um wavelengths over a reasonably long path.
Over how far of a path are you trying to do this?
What is the purpose of routing sunlight like this, rather than with mirrors etc?
What wavelengths do you need to route?
Thank you Srini Vasan , Gerhard Martens , Aleksandr A. Tarasov , Alexander Bortsov , Jason Mershon for your valuable suggestions.
I want to transport the complete wavelength of the sunlight for my indoor experiments for a distance of 02 meters. Also, it is not possible to disentangle the IR part of the concentrated light for my experiments. However, the magnitude of the sunlight can be reduced to 500X instead of 1000X.
Can I use an "optical coupler" at the focus of the lens to reduce the entry losses for fiber optical cable?
Dear Manoj Kumar Sharma ,
sorry, but
a) there is no 'optical coupler' which can violate the optical laws such as violating the NA matching
b) there is no fibre available which has constant attenuation over the solar spectrum.
You may reflect on a hollow mirrored fiber like a pipe...
and what is about free standing, focussing mirrors? - - - 2 meters is not a quite long distance.
Manoj Kumar Sharma ,
If you reduce the power of radiation when entering the optical fiber, then you do not need to worry about losses. The main choice is for optical fiber. The choice of the cross-section diameter of the light guide core is important. I wonder what power output of the optical fiber suits you. And for what purposes do You arrange the transmission of optical light power?
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