On Dec 3, 3:01=A0pm, "Michael Plante" <michael.pla...@gmail.com> wrote:> >On Dec 3, 11:08=3DA0am, Jerry Avins <j...@ieee.org> wrote: > >> Clay wrote: > >> > On Dec 3, 12:32 am, "gravelhe" <grave...@gmail.com> wrote: > >> >>> On Dec 2, 7:59=3D3DA0am, "gravelhe" <grave...@gmail.com> wrote: > >> >>>> I need an optical FIR for experiment. where can i buy this kind > of > >> >> produc=3D3D > >> >>> t? > >> >>>> Thanks! > >> >>> The hardware store. Get a piece of glass. Let the light reflect of=f> o=3D > >f > >> >>> both the 1st and 2nd surface and interfere together. This is a > simple > >> >>> comb filter. You may want to look it up under its fancier names > like > >> >>> etalon or a Fabry- Perot interferometer. I assume you have a > >> >>> monochromatic light source. > >> >>> As Jerry asks, what kind of experiment do you need to do? > >> >>> Clay > >> >>> I need the optical transversal filter as an OCDMA Encoder/Decoder > in > >> >> time domain. Thanks- Hide quoted text - > > >> >> - Show quoted text - > > >> > Then the piece of glass suffices. > > >> Avoiding interference when summing the taps requires great -- probably > >> unobtainable -- mechanical stability. > > >> Jerry > > > [...] > >He > >still hasn't revealed a whole lot of detail in what he needs > >experimentally other than "time domain." > > [...] > > I thought that initially. =A0It turns out the first line of his response =had> an extra greater-than, so it was lumped into your response on Google, and > it's therefore easy to miss: > > (part of your response, but not really) > "I need the optical transversal filter as an OCDMA Encoder/Decoder in" > > (what you probably saw, and what I initially saw) > "time domain. Thanks"- Hide quoted text - > > - Show quoted text -Thanks - I did not see the other part. The easiest way to have multiple simultaneous channels is to use different colors of light (WDM) and polarization diversity can be added to this as well. That is what is done now. The OP may want to look into spatial filtering to see how optics can be used to obtain nearly instantaeous fourier transformation and matched filtering. Clay
optical FIR product
Started by ●December 2, 2009
Reply by ●December 3, 20092009-12-03
Reply by ●December 3, 20092009-12-03
Clay wrote:> On Dec 3, 12:07 pm, Jerry Avins <j...@ieee.org> wrote: >> Clay wrote: >>> On Dec 3, 11:08 am, Jerry Avins <j...@ieee.org> wrote: >>>> Clay wrote: >>>>> On Dec 3, 12:32 am, "gravelhe" <grave...@gmail.com> wrote: >>>>>>> On Dec 2, 7:59=A0am, "gravelhe" <grave...@gmail.com> wrote: >>>>>>>> I need an optical FIR for experiment. where can i buy this kind of >>>>>> produc= >>>>>>> t? >>>>>>>> Thanks! >>>>>>> The hardware store. Get a piece of glass. Let the light reflect off of >>>>>>> both the 1st and 2nd surface and interfere together. This is a simple >>>>>>> comb filter. You may want to look it up under its fancier names like >>>>>>> etalon or a Fabry- Perot interferometer. I assume you have a >>>>>>> monochromatic light source. >>>>>>> As Jerry asks, what kind of experiment do you need to do? >>>>>>> Clay >>>>>>> I need the optical transversal filter as an OCDMA Encoder/Decoder in >>>>>> time domain. Thanks- Hide quoted text - >>>>>> - Show quoted text - >>>>> Then the piece of glass suffices. >>>> Avoiding interference when summing the taps requires great -- probably >>>> unobtainable -- mechanical stability. >>>> Jerry >>> The interference resulting from combining the taps is the point. >> Maintaining stable interference means keeping dimensions stable to about >> 60 nm. That's *hard!* >> >>> The OP wants a time domain optical filter. I gave him a simple example. >>> He still hasn't revealed a whole lot of detail in what he needs >>> experimentally other than "time domain." He can "tune" this filter by >>> changing the angle of incidence whereby effectively change the delay >>> between the 1st and 2nd reflections. If he wants something more >>> complex (more than 2 taps), he can get a hydrogen alpha filter or >>> something similar. These are made with many layers. Plus it is easy >>> enough to make holographic gratings where he can have a fair number of >>> Bragg planes (each acting like a tap in and FIR filter) What is the OP >>> really wanting? >> Jerry >> -- >> Engineering is the art of making what you want from things you can get. >> �����������������������������������������������������������������������- Hide quoted text - >> >> - Show quoted text - > > Actually it is not as hard as you think. An optical table will easily > achieve this. Back when I used to make holograms, I did this sort of > thing often on a sand box table. Yeap it is a 4 by 8 foot table (also > 1 foot deep) filled with 2000lbs of sand. The optics are mounted onto > pieces of PVC pipe stuck into the sand. You can easily adjust such > optics. I would often set up a Michelson interferometer just to see > how stable things are. Certainly if the heat or AC is blasting you > will have problems. If one of my cats walked across the floor, the > observed fringes would show the cat's walking! I would sometimes > expose holograms upwards of 5 minutes on such a table. The shutter for > the laser beam used a VU meter with a hole drilled through it and an > aluminum foil flag attached to the needle. A little current through > the meter would move the flag out of the beam.I have built two sand box tables with 2" aluminum tops and used commercial 6'x8' optical benches with servo levelers in the air vibration isolators that consisted of aluminum slabs 3"thick, with drilled and tapped holes on a regular grid. One of the latter was on the second floor, while all of the rest were used in the basement, directly on the concrete slab floor. Vibration from truck traffic a quarter mile away was often noticeable and occasionally a problem. That is what I mean by hard. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●December 4, 20092009-12-04
> >Actually it is not as hard as you think. An optical table will easily >achieve this. Back when I used to make holograms, I did this sort of >thing often on a sand box table. Yeap it is a 4 by 8 foot table (also >1 foot deep) filled with 2000lbs of sand. The optics are mounted onto >pieces of PVC pipe stuck into the sand. You can easily adjust such >optics. I would often set up a Michelson interferometer just to see >how stable things are. Certainly if the heat or AC is blasting you >will have problems. If one of my cats walked across the floor, the >observed fringes would show the cat's walking! I would sometimes >expose holograms upwards of 5 minutes on such a table. The shutter for >the laser beam used a VU meter with a hole drilled through it and an >aluminum foil flag attached to the needle. A little current through >the meter would move the flag out of the beam. > >Clay >I have known about some kinds of OCDM En/Decoders, such as Encoder based on fiber delay lines, based on SSFBGs and so on. What I need is this kind of Encoder, but we haven't the ability of doing it by ourselves. Where can I buy it ? What should I buy to make an Encoder? Is it hard? Thanks! ie: the optical transversal filter consist of 3 tunable taps,5-ps delay lines, 50-ps delay lines, 95-ps delay lines, and a combiner. Is it easy to make such kind of FIR filter?
Reply by ●December 5, 20092009-12-05
On Dec 4, 6:02=A0am, "gravelhe" <grave...@gmail.com> wrote:> >Actually it is not as hard as you think. An optical table will easily > >achieve this. Back when I used to make holograms, I did this sort of > >thing often on a sand box table. Yeap it is a 4 by 8 foot table (also > >1 foot deep) filled with 2000lbs of sand. The optics are mounted onto > >pieces of PVC pipe stuck into the sand. You can easily adjust such > >optics. I would often set up a Michelson interferometer just to see > >how stable things are. Certainly if the heat or AC is blasting you > >will have problems. If one of my cats walked across the floor, the > >observed fringes would show the cat's walking! I would sometimes > >expose holograms upwards of 5 minutes on such a table. The shutter for > >the laser beam used a VU meter with a hole drilled through it and an > >aluminum foil flag attached to the needle. A little current through > >the meter would move the flag out of the beam. > > >Clay > > =A0I have known about some kinds of OCDM En/Decoders, such as Encoder bas=ed> on fiber delay lines, based on SSFBGs and so on. What I need is this kind > of =A0Encoder, but we haven't the ability of doing it by ourselves. Where=can> I buy it ? What should I buy to make an Encoder? Is it hard? Thanks! > =A0 ie: the optical transversal filter consist of 3 tunable taps,5-ps del=ay> lines, 50-ps delay lines, 95-ps delay lines, and a combiner. Is it easy t=o> make such kind of FIR filter? =A0 =A0 =A0- Hide quoted text - > > - Show quoted text -I'm not sure where you would buy such a product off of the shelf, but if this were my project, I'd build it myself. Just imagine using several glass rods (parallepipeds) bundled together. Each rod is a tap in the FIR. Their lengths determine the delay associated with each tap and their crossectional areas determines each tap's relative weighting. The ends of the rods can have antirefection coatings for optical efficiency. You will need to collamate your light source (basically a beam expander) and have it wide enough so the light enter all rods. At the other end several lenses are used to combine the light exiting each of the rods into one source. Will this be hard, somewhat, but when you need such high powered computation, it will take some effort. Altrnatively you can have the rods all the same length but made out of different types of glass (different indices of refraction). Good Luck, Clay
Reply by ●December 5, 20092009-12-05
Clay wrote:> On Dec 4, 6:02 am, "gravelhe" <grave...@gmail.com> wrote: >>> Actually it is not as hard as you think. An optical table will easily >>> achieve this. Back when I used to make holograms, I did this sort of >>> thing often on a sand box table. Yeap it is a 4 by 8 foot table (also >>> 1 foot deep) filled with 2000lbs of sand. The optics are mounted onto >>> pieces of PVC pipe stuck into the sand. You can easily adjust such >>> optics. I would often set up a Michelson interferometer just to see >>> how stable things are. Certainly if the heat or AC is blasting you >>> will have problems. If one of my cats walked across the floor, the >>> observed fringes would show the cat's walking! I would sometimes >>> expose holograms upwards of 5 minutes on such a table. The shutter for >>> the laser beam used a VU meter with a hole drilled through it and an >>> aluminum foil flag attached to the needle. A little current through >>> the meter would move the flag out of the beam. >>> Clay >> I have known about some kinds of OCDM En/Decoders, such as Encoder based >> on fiber delay lines, based on SSFBGs and so on. What I need is this kind >> of Encoder, but we haven't the ability of doing it by ourselves. Where can >> I buy it ? What should I buy to make an Encoder? Is it hard? Thanks! >> ie: the optical transversal filter consist of 3 tunable taps,5-ps delay >> lines, 50-ps delay lines, 95-ps delay lines, and a combiner. Is it easy to >> make such kind of FIR filter? - Hide quoted text - >> >> - Show quoted text - > > I'm not sure where you would buy such a product off of the shelf, but > if this were my project, I'd build it myself. Just imagine using > several glass rods (parallepipeds) bundled together. Each rod is a tap > in the FIR. Their lengths determine the delay associated with each tap > and their crossectional areas determines each tap's relative > weighting. The ends of the rods can have antirefection coatings for > optical efficiency. You will need to collamate your light source > (basically a beam expander) and have it wide enough so the light enter > all rods. At the other end several lenses are used to combine the > light exiting each of the rods into one source. Will this be hard, > somewhat, but when you need such high powered computation, it will > take some effort. Altrnatively you can have the rods all the same > length but made out of different types of glass (different indices of > refraction).It seems to me that the construction difficulty here is similar to that of the quartz polarizing monochromator described by Albert Ingalls in Scientific American's "The Amateur Astronomer" (Later, "The Amateur Scientist".) That instrument is tuned by varying the power to a heater. Iy is described in this set: http://www.willbell.com/tm/tm7.htm. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●December 5, 20092009-12-05
> >Actually it is not as hard as you think. An optical table will easily >achieve this. Back when I used to make holograms, I did this sort of >thing often on a sand box table. Yeap it is a 4 by 8 foot table (also >1 foot deep) filled with 2000lbs of sand. The optics are mounted onto >pieces of PVC pipe stuck into the sand. You can easily adjust such >optics. I would often set up a Michelson interferometer just to see >how stable things are. Certainly if the heat or AC is blasting you >will have problems. If one of my cats walked across the floor, the >observed fringes would show the cat's walking! I would sometimes >expose holograms upwards of 5 minutes on such a table. The shutter for >the laser beam used a VU meter with a hole drilled through it and an >aluminum foil flag attached to the needle. A little current through >the meter would move the flag out of the beam. > >Clay >I need the optical transversal filter consisting of 3 tunable taps, 5-ps delay lines, 55-ps dalay lines, 95-ps delay lines, and a combiner, all of which are monolithically integrated as a planar lightwave circuit. Is it hard to achieve if we do it by ourselves? Can I buy this kind of product? I have known some kinds of optical En/Decoders in some papers. ie, Encoder based on optical fiber delay lines, based on SSFBGs, or based on AWG and so on. Thanks very much!
Reply by ●December 7, 20092009-12-07
On Dec 5, 10:48�am, Jerry Avins <j...@ieee.org> wrote:> Clay wrote: > > On Dec 4, 6:02 am, "gravelhe" <grave...@gmail.com> wrote: > >>> Actually it is not as hard as you think. An optical table will easily > >>> achieve this. Back when I used to make holograms, I did this sort of > >>> thing often on a sand box table. Yeap it is a 4 by 8 foot table (also > >>> 1 foot deep) filled with 2000lbs of sand. The optics are mounted onto > >>> pieces of PVC pipe stuck into the sand. You can easily adjust such > >>> optics. I would often set up a Michelson interferometer just to see > >>> how stable things are. Certainly if the heat or AC is blasting you > >>> will have problems. If one of my cats walked across the floor, the > >>> observed fringes would show the cat's walking! I would sometimes > >>> expose holograms upwards of 5 minutes on such a table. The shutter for > >>> the laser beam used a VU meter with a hole drilled through it and an > >>> aluminum foil flag attached to the needle. A little current through > >>> the meter would move the flag out of the beam. > >>> Clay > >> �I have known about some kinds of OCDM En/Decoders, such as Encoder based > >> on fiber delay lines, based on SSFBGs and so on. What I need is this kind > >> of �Encoder, but we haven't the ability of doing it by ourselves. Where can > >> I buy it ? What should I buy to make an Encoder? Is it hard? Thanks! > >> � ie: the optical transversal filter consist of 3 tunable taps,5-ps delay > >> lines, 50-ps delay lines, 95-ps delay lines, and a combiner. Is it easy to > >> make such kind of FIR filter? � � �- Hide quoted text - > > >> - Show quoted text - > > > I'm not sure where you would buy such a product off of the shelf, but > > if this were my project, I'd build it myself. Just imagine using > > several glass rods (parallepipeds) bundled together. Each rod is a tap > > in the FIR. Their lengths determine the delay associated with each tap > > and their crossectional areas determines each tap's relative > > weighting. The ends of the rods can have antirefection coatings for > > optical efficiency. You will need to collamate your light source > > (basically a beam expander) and have it wide enough so the light enter > > all rods. At the other end several lenses are used to combine the > > light exiting each of the rods into one source. Will this be hard, > > somewhat, but when you need such high powered computation, it will > > take some effort. Altrnatively you can have the rods all the same > > length but made out of different types of glass (different indices of > > refraction). > > It seems to me that the construction difficulty here is similar to that > of the quartz polarizing monochromator described by Albert Ingalls in > Scientific American's "The Amateur Astronomer" (Later, "The Amateur > Scientist".) That instrument is tuned by varying the power to a heater. > Iy is described in this set:http://www.willbell.com/tm/tm7.htm. > > Jerry > -- > Engineering is the art of making what you want from things you can get. > �����������������������������������������������������������������������- Hide quoted text - > > - Show quoted text -It will involve some work, but is doable. He is really only worrying about the modulation and not the carrier. You can have the light enter the parallel array of light pipes from a slight angle so the interference fringes average out. Clay p.s. I like Willman Bell books. I just got another one of their books just this week.
Reply by ●December 7, 20092009-12-07
>I'm not sure where you would buy such a product off of the shelf, but >if this were my project, I'd build it myself. Just imagine using >several glass rods (parallepipeds) bundled together. Each rod is a tap >in the FIR. Their lengths determine the delay associated with each tap >and their crossectional areas determines each tap's relative >weighting. The ends of the rods can have antirefection coatings for >optical efficiency. You will need to collamate your light source >(basically a beam expander) and have it wide enough so the light enter >all rods. At the other end several lenses are used to combine the >light exiting each of the rods into one source. Will this be hard, >somewhat, but when you need such high powered computation, it will >take some effort. Altrnatively you can have the rods all the same >length but made out of different types of glass (different indices of >refraction). > >Good Luck, >Clay >Thanks very much! Maybe I can do it by myself. The optical transversal filter will be consist of a splitter,3 fiber delay lines(different length),and a coupler. optical pulse will be split into 3 parts, each part as the input of one fiber delay line, and then they will be combined together by the coupler after different delays in 3 fiber delay lines. There is still one problem. The optical pulse initially is not monochromatic, and the split pulse is still multi wavelength, so the fiber delay line will process several wavelengths pulse simultaneously. In such case,what should i pay more attentions to make such equipment?
Reply by ●December 7, 20092009-12-07
gravelhe wrote:> The optical transversal > filter will be consist of a splitter,3 fiber delay lines(different > length),and a coupler. optical pulse will be split into 3 parts, each part > as the input of one fiber delay line, and then they will be combined > together by the coupler after different delays in 3 fiber delay lines.There is a little problem here: you can add beams, but you can't subtract them. There is no "negative" light.> There is still one problem. The optical pulse initially is not > monochromatic, and the split pulse is still multi wavelength, so the fiber > delay line will process several wavelengths pulse simultaneously. In such > case,what should i pay more attentions to make such equipment?Well, if you want to do coherent combining of the beams, that makes things much more difficult even if you use single mode fibers. VLV
Reply by ●December 8, 20092009-12-08
On Dec 7, 10:55�pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote:> gravelhe wrote: > > The optical �transversal > > filter will be consist of a splitter,3 fiber delay lines(different > > length),and a coupler. optical pulse will be split into 3 parts, each part > > as the input of one fiber delay line, and then they will be combined > > together by the coupler after different delays in 3 fiber delay lines. > > There is a little problem here: you can add beams, but you can't > subtract them. There is no "negative" light. > > > �There is still one problem. The optical pulse initially is not > > monochromatic, and the split pulse is still multi wavelength, so the fiber > > delay line will process several wavelengths pulse simultaneously. In such > > case,what should i pay more attentions to make such equipment? > > Well, if you want to do coherent combining of the beams, that makes > things much more difficult even if you use single mode fibers. > > VLVIt depends if his 3 taps all have positive coefs. If not, he can look into an AM radio sort of thing where the modulation is offset so the multiplication is always by positive values. If you want to get really fancy, you can subtract light using either Kerr or Pockels cells. Clay
