## speed of light timer

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• Hi there, I need a device which can measure the fluctuations, in a light ray, with the speed of light. I mean, I need to know if at second 10^-8 (ten to power
Message 1 of 19 , Oct 31, 2005
Hi there,

I need a device which can measure the fluctuations, in a light ray,
with the speed of light.

I mean, I need to know if at second 10^-8 (ten to power minus 8) I have
a fluctuation in a light ray. I'm not interested to compute the power
of that ray. I'm just interested to know if at a given moment in time
(very, very small) it was or not a fluctuation in the intensity of that
ray.

Is this possible?

Thanks,
Michael
• On Tue, 01 Nov 2005 07:02:15 +0100, computer50000 ... Well, fast scopes certainly go down there in the nanosecond range. I m not sure about optical receivers,
Message 2 of 19 , Nov 1, 2005
On Tue, 01 Nov 2005 07:02:15 +0100, computer50000
<computer50000@...> wrote:

> Hi there,
> I need a device which can measure the fluctuations, in a light ray,
> with the speed of light.
> I mean, I need to know if at second 10^-8 (ten to power minus 8) I have
> a fluctuation in a light ray. I'm not interested to compute the power
> of that ray. I'm just interested to know if at a given moment in time
> (very, very small) it was or not a fluctuation in the intensity of that
> ray.
> Is this possible?
> Thanks,
> Michael

Well, fast scopes certainly go down there in the nanosecond range.
I'm not sure about optical receivers, if any diodes are fast enough, but i
would expect.

But i don't fully understand what you need. When do you need to measure?
How do you know when to expect a fluctuation? Is it repetitive or single
shot?

In short, what do you want to do?

As for building something, well, to measure the time with ns accuracy you
need a timer running at a 1Ghz clock. While that's not insane it is
slightly out of my homebrew experience.

Best bet for me seems to be a scope. You need some form of event to
trigger it when you expect the light fluctutation. Maybe if you use a
laser beam you can have a diode at the laser, giving you a "start" signal,
and then the beam goes away to a mirror, and you measure the reflected
light too. This would give you the distance between laser and mirror *2 on
the screen. Remember the signals in the coax cables will be somewhat
slower than speed of light, so you need them short and equal length.

Need more details to suggest any hardware.

ST
• Hi - Also, the rise time of your detector will play into this - this is the time required for the new signal seen by the detector. If its slower than your
Message 3 of 19 , Nov 1, 2005
Hi - Also, the rise time of your detector will play into this - this is the
time required for the new signal seen by the detector. If its slower than
your observed phenomea, then I doubt you'll see it, or get much accuracy.

Just my 0.02 cents/euros worth....

Bruce
----- Original Message -----
From: "Stefan Trethan" <stefan_trethan@...>
To: <Electronics_101@yahoogroups.com>
Sent: Tuesday, November 01, 2005 3:52 AM
Subject: Re: [Electronics_101] speed of light timer

> On Tue, 01 Nov 2005 07:02:15 +0100, computer50000
> <computer50000@...> wrote:
>
>> Hi there,
>> I need a device which can measure the fluctuations, in a light ray,
>> with the speed of light.
>> I mean, I need to know if at second 10^-8 (ten to power minus 8) I have
>> a fluctuation in a light ray. I'm not interested to compute the power
>> of that ray. I'm just interested to know if at a given moment in time
>> (very, very small) it was or not a fluctuation in the intensity of that
>> ray.
>> Is this possible?
>> Thanks,
>> Michael
>
>
> Well, fast scopes certainly go down there in the nanosecond range.
> I'm not sure about optical receivers, if any diodes are fast enough, but i
> would expect.
>
>
> But i don't fully understand what you need. When do you need to measure?
> How do you know when to expect a fluctuation? Is it repetitive or single
> shot?
>
> In short, what do you want to do?
>
> As for building something, well, to measure the time with ns accuracy you
> need a timer running at a 1Ghz clock. While that's not insane it is
> slightly out of my homebrew experience.
>
> Best bet for me seems to be a scope. You need some form of event to
> trigger it when you expect the light fluctutation. Maybe if you use a
> laser beam you can have a diode at the laser, giving you a "start" signal,
> and then the beam goes away to a mirror, and you measure the reflected
> light too. This would give you the distance between laser and mirror *2 on
> the screen. Remember the signals in the coax cables will be somewhat
> slower than speed of light, so you need them short and equal length.
>
>
> Need more details to suggest any hardware.
>
>
> ST
>
>
>
>
>
>
>
>
>
>
>
• Dear Stefan, I m sending a light ray with a laser. The ray will follow some complicated path. Sometimes, the ray will be splitted into 2 rays and each of them
Message 4 of 19 , Nov 1, 2005
Dear Stefan,

I'm sending a light ray with a laser. The ray will follow some
complicated path. Sometimes, the ray will be splitted into 2 rays and
each of them will follow some path.

All rays have the same destination, but they will reach there at
different moments in time (probably), depending on the length of the
path that they have followed.

I know the exact moment when a particular ray should get to the
destination, but I need to know if it actually got there (or it has
got stuck somewhere on the path).

This is why I need some device, which can tell me if there is a
fluctuation in the light, at the destination point, at a given moment
in time (that moment must be specified with high precision ~ 10^-9).
If I have a fluctuation in the signat at that moment I know for sure
that the particular ray which I was expecting has arrived there.

Thanks,
Michael

--- In Electronics_101@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
>
> On Tue, 01 Nov 2005 07:02:15 +0100, computer50000
> <computer50000@y...> wrote:
>
> > Hi there,
> > I need a device which can measure the fluctuations, in a light
ray,
> > with the speed of light.
> > I mean, I need to know if at second 10^-8 (ten to power minus 8)
I have
> > a fluctuation in a light ray. I'm not interested to compute the
power
> > of that ray. I'm just interested to know if at a given moment in
time
> > (very, very small) it was or not a fluctuation in the intensity
of that
> > ray.
> > Is this possible?
> > Thanks,
> > Michael
>
>
> Well, fast scopes certainly go down there in the nanosecond range.
> I'm not sure about optical receivers, if any diodes are fast
enough, but i
> would expect.
>
>
> But i don't fully understand what you need. When do you need to
measure?
> How do you know when to expect a fluctuation? Is it repetitive or
single
> shot?
>
> In short, what do you want to do?
>
> As for building something, well, to measure the time with ns
accuracy you
> need a timer running at a 1Ghz clock. While that's not insane it
is
> slightly out of my homebrew experience.
>
> Best bet for me seems to be a scope. You need some form of event
to
> trigger it when you expect the light fluctutation. Maybe if you use
a
> laser beam you can have a diode at the laser, giving you a "start"
signal,
> and then the beam goes away to a mirror, and you measure the
reflected
> light too. This would give you the distance between laser and
mirror *2 on
> the screen. Remember the signals in the coax cables will be
somewhat
> slower than speed of light, so you need them short and equal length.
>
>
> Need more details to suggest any hardware.
>
>
> ST
>
• Well, do you need to make this a automated process or can you take manual measurements (look at a scope screen)? I would think that a fast oscilloscope (with
Message 5 of 19 , Nov 1, 2005
Well, do you need to make this a automated process or can you take manual
measurements (look at a scope screen)?

I would think that a fast oscilloscope (with under 1ns risetime) and a
optical receiver with a risetime in the same range will be the solution.
You would need a real-time storage scope if the signal is non-repetitive.
On the scope screen you would then see pulses, or steps, at the times
where different beams arrive at the receiver. You would need to use one
beam to trigger the scope (one which is always arriving before the
interesting one might come).

I dunno what your budget is, it can be done in a very expensive manner,
but probably also in a somewhat cheap manner. Ideally you could repeat the
process repetitively with the same result, then you wouldn't need real
time storage, which would make the scope much easier to get or borrow. The
optical receiver can be bought for \$\$\$\$\$ or certainly be built much
cheaper with a fast photodiode. I mean you can get a 1ns rise/fall diode
at mouser these days, i would expect a even better diode is still
affordable. Of course you need a bias/amplifier circuit too that is fast

Getting a scope with better than 1ns risetime, and single shot capability
at that, would appear to be the most expensive thing, otoh you can rent
them and it is certainly easier to find than the photoreceiver.

ST

On Tue, 01 Nov 2005 12:38:42 +0100, computer50000
<computer50000@...> wrote:

> Dear Stefan,
> I'm sending a light ray with a laser. The ray will follow some
> complicated path. Sometimes, the ray will be splitted into 2 rays and
> each of them will follow some path.
> All rays have the same destination, but they will reach there at
> different moments in time (probably), depending on the length of the
> path that they have followed.
> I know the exact moment when a particular ray should get to the
> destination, but I need to know if it actually got there (or it has
> got stuck somewhere on the path).
> This is why I need some device, which can tell me if there is a
> fluctuation in the light, at the destination point, at a given moment
> in time (that moment must be specified with high precision ~ 10^-9).
> If I have a fluctuation in the signat at that moment I know for sure
> that the particular ray which I was expecting has arrived there.
> Thanks,
> Michael
• Thanks Stefan, I just need to know if it was a fluctuation in the intensity of light. Is not important whether I read this manually or by using an computer.
Message 6 of 19 , Nov 1, 2005
Thanks Stefan,

I just need to know if it was a fluctuation in the intensity of
light. Is not important whether I read this manually or by using an
computer. However, because the time is very very short probably I
need to store it. And another reason is that probably there will be
many, many signals (I mean many fluctuations). But, at a given moment
I know that there is only one fluctuation.

The signal is non repetitive.

The price is not important at this moment. First of all I'm looking
for a solution and then I will look to the implementation.

Could you give me some more details on how I use the optical receiver
and the oscilloscope. I'm a computer scientist which does not know
too many things about electronics stuff.

Thanks,

--- In Electronics_101@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
>
> Well, do you need to make this a automated process or can you take
manual
> measurements (look at a scope screen)?
>
> I would think that a fast oscilloscope (with under 1ns risetime)
and a
> optical receiver with a risetime in the same range will be the
solution.
> You would need a real-time storage scope if the signal is non-
repetitive.
> On the scope screen you would then see pulses, or steps, at the
times
> where different beams arrive at the receiver. You would need to use
one
> beam to trigger the scope (one which is always arriving before the
> interesting one might come).
>
> I dunno what your budget is, it can be done in a very expensive
manner,
> but probably also in a somewhat cheap manner. Ideally you could
repeat the
> process repetitively with the same result, then you wouldn't need
real
> time storage, which would make the scope much easier to get or
borrow. The
> optical receiver can be bought for \$\$\$\$\$ or certainly be built
much
> cheaper with a fast photodiode. I mean you can get a 1ns rise/fall
diode
> at mouser these days, i would expect a even better diode is still
> affordable. Of course you need a bias/amplifier circuit too that is
fast
>
> Getting a scope with better than 1ns risetime, and single shot
capability
> at that, would appear to be the most expensive thing, otoh you can
rent
> them and it is certainly easier to find than the photoreceiver.
>
> ST
>
>
> On Tue, 01 Nov 2005 12:38:42 +0100, computer50000
> <computer50000@y...> wrote:
>
> > Dear Stefan,
> > I'm sending a light ray with a laser. The ray will follow some
> > complicated path. Sometimes, the ray will be splitted into 2 rays
and
> > each of them will follow some path.
> > All rays have the same destination, but they will reach there at
> > different moments in time (probably), depending on the length of
the
> > path that they have followed.
> > I know the exact moment when a particular ray should get to the
> > destination, but I need to know if it actually got there (or it
has
> > got stuck somewhere on the path).
> > This is why I need some device, which can tell me if there is a
> > fluctuation in the light, at the destination point, at a given
moment
> > in time (that moment must be specified with high precision ~ 10^-
9).
> > If I have a fluctuation in the signat at that moment I know for
sure
> > that the particular ray which I was expecting has arrived there.
> > Thanks,
> > Michael
>
• On Tue, 01 Nov 2005 13:51:50 +0100, computer50000 ... You can buy off-the shelf photoreceivers that hook straight to the scope, and a power supply. The scope
Message 7 of 19 , Nov 1, 2005
On Tue, 01 Nov 2005 13:51:50 +0100, computer50000
<computer50000@...> wrote:

>
> The price is not important at this moment. First of all I'm looking
> for a solution and then I will look to the implementation.
> Could you give me some more details on how I use the optical receiver
> and the oscilloscope. I'm a computer scientist which does not know
> too many things about electronics stuff.
> Thanks,

You can buy off-the shelf photoreceivers that hook straight to the scope,
and a power supply.

The scope could be a digital storage scope with under 1ns risetime, and
over 1Gs. That would give resolution in the 10^-9 ballpark. Most scopes
can be hooked to a computer, which you can use to document measurements or
even use to execute and interpret the measurement automatically.

Any optical research/experimentation facility will have such stuff in use,
ultrafast optical pulses are the rage right now, so most universities
could allow you to see the required gear so you can get a closer idea.

ST
• ... What about super high speed photography ? I remember seeing a photo of a pulse of light. there was a matrix of mirrors and the photo caught the pulse in
Message 8 of 19 , Nov 1, 2005
--- In Electronics_101@yahoogroups.com, "computer50000"
<computer50000@y...> wrote:
>
>
> Dear Stefan,
>
> I'm sending a light ray with a laser. The ray will follow some
> complicated path. Sometimes, the ray will be splitted into 2 rays and
> each of them will follow some path.
>
> All rays have the same destination, but they will reach there at
> different moments in time (probably), depending on the length of the
> path that they have followed.
>
> I know the exact moment when a particular ray should get to the
> destination, but I need to know if it actually got there (or it has
> got stuck somewhere on the path).
>
> This is why I need some device, which can tell me if there is a
> fluctuation in the light, at the destination point, at a given moment
> in time (that moment must be specified with high precision ~ 10^-9).
> If I have a fluctuation in the signat at that moment I know for sure
> that the particular ray which I was expecting has arrived there.
>
> Thanks,
> Michael

What about super high speed photography ?

I remember seeing a photo of a pulse of light.

there was a matrix of mirrors and the photo caught the pulse in the
middle of the matrix as it was bouncing from one to the next.

Probably way tooo complex for lab testing, but a great photo for the
wow factor.

Dave
• Dear Dave, Could you give me some more information on where could I find that picture? Thanks, Michael
Message 9 of 19 , Nov 1, 2005
Dear Dave,

Could you give me some more information on where could I find that
picture?

Thanks,
Michael

> What about super high speed photography ?
>
> I remember seeing a photo of a pulse of light.
>
> there was a matrix of mirrors and the photo caught the pulse in the
> middle of the matrix as it was bouncing from one to the next.
>
> Probably way tooo complex for lab testing, but a great photo for the
> wow factor.
>
> Dave
>
• On Tue, 01 Nov 2005 16:29:00 +0100, computer50000 ... I would appreciate that too, it must be quite hard to do considering the light has to travel to the
Message 10 of 19 , Nov 1, 2005
On Tue, 01 Nov 2005 16:29:00 +0100, computer50000
<computer50000@...> wrote:

> Dear Dave,
> Could you give me some more information on where could I find that
> picture?
> Thanks,
> Michael

I would appreciate that too, it must be quite hard to do considering the
light has to travel to the camera as well.

ST
• I don t know much about optical equipment, but I have made circuits that detect light intensity. A photodiode, wired in a transresistive mode, can be made to
Message 11 of 19 , Nov 1, 2005
I don't know much about optical equipment, but I have made circuits that detect light intensity. A photodiode, wired in a transresistive mode, can be made to have incredibly high gains, allowing even the smallest of light changes to be detected. The speed at which the circuit functions will be dependent on the type of op amp you use.

computer50000 <computer50000@...> wrote:
Hi there,

I need a device which can measure the fluctuations, in a light ray,
with the speed of light.

I mean, I need to know if at second 10^-8 (ten to power minus 8) I have
a fluctuation in a light ray. I'm not interested to compute the power
of that ray. I'm just interested to know if at a given moment in time
(very, very small) it was or not a fluctuation in the intensity of that
ray.

Is this possible?

Thanks,
Michael

• I also don t know if the light is the best solution to choose. Right now I m looking for some solutions to my problem. What I know is that I send a signal
Message 12 of 19 , Nov 1, 2005
I also don't know if the light is the best solution to choose. Right
now I'm looking for some solutions to my problem. What I know is that
I send a signal (probably a light ray) into some device... the light
will be divided into some nodes of the device and because of that I
will have multiple rays at the destination. But I know the moment
when a particular ray will arrive there. I need only to know whether
that particular ray has arrived there (or it was stuck somewhere).

Do you think that I could use another kind of signal (instead of
light). At a theoretical level I work with signals, but if I want to
make an implementation probably (???) the light is the best. Because
I need SPEED.

Any suggestions are welcomed !

Thanks,
M

--- In Electronics_101@yahoogroups.com, One Two <smjones1969@s...>
wrote:
>
> I don't know much about optical equipment, but I have made circuits
that detect light intensity. A photodiode, wired in a transresistive
mode, can be made to have incredibly high gains, allowing even the
smallest of light changes to be detected. The speed at which the
circuit functions will be dependent on the type of op amp you use.
>
> computer50000 <computer50000@y...> wrote:Hi there,
>
> I need a device which can measure the fluctuations, in a light ray,
> with the speed of light.
>
> I mean, I need to know if at second 10^-8 (ten to power minus 8) I
have
> a fluctuation in a light ray. I'm not interested to compute the
power
> of that ray. I'm just interested to know if at a given moment in
time
> (very, very small) it was or not a fluctuation in the intensity of
that
> ray.
>
> Is this possible?
>
> Thanks,
> Michael
>
>
>
>
>
>
> ---------------------------------
>
>
> Visit your group "Electronics_101" on the web.
>
> To unsubscribe from this group, send an email to:
> Electronics_101-unsubscribe@yahoogroups.com
>
> Your use of Yahoo! Groups is subject to the Yahoo! Terms of
Service.
>
>
> ---------------------------------
>
• If the device can be simulated using a electric net i would simply use electric pulses. They propagate only a little bit slower than light, and can be
Message 13 of 19 , Nov 1, 2005
If the "device" can be simulated using a electric net i would simply use
electric pulses.
They propagate only a little bit slower than light, and can be measured
somewhat easier IMO.
You'd create them with a fast pulse generator, and see them with a scope.

However it might be tricky to build whatever function you need
electrically, especially with limited understanding of HF electronics.

Other things such as radio waves, sound, pressure waves, or even materials
like a flow of fluid or gas might be possible, but it really depends on
what you want to look at.

ST

On Tue, 01 Nov 2005 18:12:20 +0100, computer50000
<computer50000@...> wrote:

> I also don't know if the light is the best solution to choose. Right
> now I'm looking for some solutions to my problem. What I know is that
> I send a signal (probably a light ray) into some device... the light
> will be divided into some nodes of the device and because of that I
> will have multiple rays at the destination. But I know the moment
> when a particular ray will arrive there. I need only to know whether
> that particular ray has arrived there (or it was stuck somewhere).
> Do you think that I could use another kind of signal (instead of
> light). At a theoretical level I work with signals, but if I want to
> make an implementation probably (???) the light is the best. Because
> I need SPEED.
> Any suggestions are welcomed !
> Thanks,
> M
• Could you give me some more information on using electric pulses? Please keep in mind that speed is a priority in my system. Thanks, M ... simply use ...
Message 14 of 19 , Nov 1, 2005

Please keep in mind that speed is a priority in my system.

Thanks,
M

--- In Electronics_101@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
>
> If the "device" can be simulated using a electric net i would
simply use
> electric pulses.
> They propagate only a little bit slower than light, and can be
measured
> somewhat easier IMO.
> You'd create them with a fast pulse generator, and see them with a
scope.
>
> However it might be tricky to build whatever function you need
> electrically, especially with limited understanding of HF
electronics.
>
> Other things such as radio waves, sound, pressure waves, or even
materials
> like a flow of fluid or gas might be possible, but it really
depends on
> what you want to look at.
>
>
>
> ST
>
>
>
> On Tue, 01 Nov 2005 18:12:20 +0100, computer50000
> <computer50000@y...> wrote:
>
> > I also don't know if the light is the best solution to choose.
Right
> > now I'm looking for some solutions to my problem. What I know is
that
> > I send a signal (probably a light ray) into some device... the
light
> > will be divided into some nodes of the device and because of that
I
> > will have multiple rays at the destination. But I know the moment
> > when a particular ray will arrive there. I need only to know
whether
> > that particular ray has arrived there (or it was stuck somewhere).
> > Do you think that I could use another kind of signal (instead of
> > light). At a theoretical level I work with signals, but if I want
to
> > make an implementation probably (???) the light is the best.
Because
> > I need SPEED.
> > Any suggestions are welcomed !
> > Thanks,
> > M
>
• On Tue, 01 Nov 2005 18:45:45 +0100, computer50000 ... You send a pulse into a line, it travels along it, imagine it like a water wave. At the ends of the line
Message 15 of 19 , Nov 1, 2005
On Tue, 01 Nov 2005 18:45:45 +0100, computer50000
<computer50000@...> wrote:

> Could you give me some more information on using electric pulses?
> Please keep in mind that speed is a priority in my system.
> Thanks,
> M

You send a pulse into a line, it travels along it, imagine it like a water
wave. At the ends of the line it will be reflected unless there's the
right termination resistance.

Not much to it really without going into serious maths which i'm not going
to do. Electric pulses travel in the ballpark of 2E8m/s, i would say that
is plenty fast.

look with google for pulses and transmission line.

ST
• I m curious, are you Michael or Laura? I see the same posts in sci.electronics.design and sci.physics but signed Laura. I mean exactly the same post, word for
Message 16 of 19 , Nov 1, 2005
I'm curious, are you Michael or Laura? I see the same posts in
sci.electronics.design and sci.physics but signed Laura.

I mean exactly the same post, word for word, comma for comma.

Steve Greenfield

--- In Electronics_101@yahoogroups.com, "computer50000"
<computer50000@y...> wrote:
>
> Hi there,
>
> I need a device which can measure the fluctuations, in a light ray,
> with the speed of light.
>
> I mean, I need to know if at second 10^-8 (ten to power minus 8) I have
> a fluctuation in a light ray. I'm not interested to compute the power
> of that ray. I'm just interested to know if at a given moment in time
> (very, very small) it was or not a fluctuation in the intensity of that
> ray.
>
> Is this possible?
>
> Thanks,
> Michael
>
• Just in case you didn t know, light and the electrical signal propagate at roughly the same speed. I seriously doubt you would need to be concerned in the
Message 17 of 19 , Nov 1, 2005
Just in case you didn't know, light and the electrical signal propagate at roughly the same speed. I seriously doubt you would need to be concerned in the small difference in speed between the two for your application. If you instead use an electrical signal, you will gain the advantages of it staying in the medium and an extreme variety of devices to choose from to work with your signal.

computer50000 <computer50000@...> wrote:
I also don't know if the light is the best solution to choose. Right
now I'm looking for some solutions to my problem. What I know is that
I send a signal (probably a light ray) into some device... the light
will be divided into some nodes of the device and because of that I
will have multiple rays at the destination. But I know the moment
when a particular ray will arrive there. I need only to know whether
that particular ray has arrived there (or it was stuck somewhere).

Do you think that I could use another kind of signal (instead of
light). At a theoretical level I work with signals, but if I want to
make an implementation probably (???) the light is the best. Because
I need SPEED.

Any suggestions are welcomed !

Thanks,
M

--- In Electronics_101@yahoogroups.com, One Two <smjones1969@s...>
wrote:
>
> I don't know much about optical equipment, but I have made circuits
that detect light intensity. A photodiode, wired in a transresistive
mode, can be made to have incredibly high gains, allowing even the
smallest of light changes to be detected. The speed at which the
circuit functions will be dependent on the type of op amp you use.
>
> computer50000 <computer50000@y...> wrote:Hi there,
>
> I need a device which can measure the fluctuations, in a light ray,
> with the speed of light.
>
> I mean, I need to know if at second 10^-8 (ten to power minus 8) I
have
> a fluctuation in a light ray. I'm not interested to compute the
power
> of that ray. I'm just interested to know if at a given moment in
time
> (very, very small) it was or not a fluctuation in the intensity of
that
> ray.
>
> Is this possible?
>
> Thanks,
> Michael
>
>
>
>
>
>
> ---------------------------------
>
>
>     Visit your group "Electronics_101" on the web.
>
>     To unsubscribe from this group, send an email to:
>  Electronics_101-unsubscribe@yahoogroups.com
>
>     Your use of Yahoo! Groups is subject to the Yahoo! Terms of
Service.
>
>
> ---------------------------------
>

• It is worth checking VOP (velocity of propogation) in any cable or wire you select. It is not unusual for VOP to be around .8 or 80% of the speed of light,
Message 18 of 19 , Nov 2, 2005
It is worth checking VOP (velocity of propogation) in any cable or
wire you select. It is not unusual for VOP to be around .8 or 80%
of the speed of light, maybe even down to 0.7. See
http://www.picwire.com/technical/paper2.html

The VOP in a twisted pair cable might be around 0.65. See
http://www.tscm.com/riprcop.html

At VOP of 0.65, I don't consider that anywhere close to the speed of
light.

Knowing VOP is important in electrical design because signals do not
arrive in zero time. It is not unusual to skew a clock signal by
adding a length of wire to slow it down and realign it with the
data. Consider the multicabinet mainframe computer. Here
realignment is critical.

--- In Electronics_101@yahoogroups.com, One Two <smjones1969@s...>
wrote:
>
> Just in case you didn't know, light and the electrical signal
propagate at roughly the same speed. I seriously doubt you would
need to be concerned in the small difference in speed between the
you will gain the advantages of it staying in the medium and an
extreme variety of devices to choose from to work with your signal.
>
> computer50000 <computer50000@y...> wrote:I also don't know if the
light is the best solution to choose. Right
> now I'm looking for some solutions to my problem. What I know is
that
> I send a signal (probably a light ray) into some device... the
light
> will be divided into some nodes of the device and because of that
I
> will have multiple rays at the destination. But I know the moment
> when a particular ray will arrive there. I need only to know
whether
> that particular ray has arrived there (or it was stuck somewhere).
>
> Do you think that I could use another kind of signal (instead of
> light). At a theoretical level I work with signals, but if I want
to
> make an implementation probably (???) the light is the best.
Because
> I need SPEED.
>
> Any suggestions are welcomed !
>
> Thanks,
> M
>
> --- In Electronics_101@yahoogroups.com, One Two <smjones1969@s...>
> wrote:
> >
> > I don't know much about optical equipment, but I have made
circuits
> that detect light intensity. A photodiode, wired in a
transresistive
> mode, can be made to have incredibly high gains, allowing even the
> smallest of light changes to be detected. The speed at which the
> circuit functions will be dependent on the type of op amp you use.
> >
> > computer50000 <computer50000@y...> wrote:Hi there,
> >
> > I need a device which can measure the fluctuations, in a light
ray,
> > with the speed of light.
> >
> > I mean, I need to know if at second 10^-8 (ten to power minus 8)
I
> have
> > a fluctuation in a light ray. I'm not interested to compute the
> power
> > of that ray. I'm just interested to know if at a given moment in
> time
> > (very, very small) it was or not a fluctuation in the intensity
of
> that
> > ray.
> >
> > Is this possible?
> >
> > Thanks,
> > Michael
> >
> >
> >
> >
> >
> >
> > ---------------------------------
> >
> >
> > Visit your group "Electronics_101" on the web.
> >
> > To unsubscribe from this group, send an email to:
> > Electronics_101-unsubscribe@yahoogroups.com
> >
> > Your use of Yahoo! Groups is subject to the Yahoo! Terms of
> Service.
> >
> >
> > ---------------------------------
> >
>
>
>
>
>
>
>
> ---------------------------------
>
>
> Visit your group "Electronics_101" on the web.
>
> To unsubscribe from this group, send an email to:
> Electronics_101-unsubscribe@yahoogroups.com
>
> Your use of Yahoo! Groups is subject to the Yahoo! Terms of
Service.
>
>
> ---------------------------------
>
• I cannot open the first link. Could you ckeck it again? Thanks, M ... of ... not ... ... the ... use. ... 8) ... in
Message 19 of 19 , Nov 2, 2005
I cannot open the first link. Could you ckeck it again?
Thanks,
M

--- In Electronics_101@yahoogroups.com, "rtstofer" <rstofer@p...>
wrote:
>
>
> It is worth checking VOP (velocity of propogation) in any cable or
> wire you select. It is not unusual for VOP to be around .8 or 80%
> of the speed of light, maybe even down to 0.7. See
> http://www.picwire.com/technical/paper2.html
>
> The VOP in a twisted pair cable might be around 0.65. See
> http://www.tscm.com/riprcop.html
>
> At VOP of 0.65, I don't consider that anywhere close to the speed
of
> light.
>
> Knowing VOP is important in electrical design because signals do
not
> arrive in zero time. It is not unusual to skew a clock signal by
> adding a length of wire to slow it down and realign it with the
> data. Consider the multicabinet mainframe computer. Here
> realignment is critical.
>
>
>
> --- In Electronics_101@yahoogroups.com, One Two <smjones1969@s...>
> wrote:
> >
> > Just in case you didn't know, light and the electrical signal
> propagate at roughly the same speed. I seriously doubt you would
> need to be concerned in the small difference in speed between the
> two for your application. If you instead use an electrical signal,
> you will gain the advantages of it staying in the medium and an
> extreme variety of devices to choose from to work with your signal.
> >
> > computer50000 <computer50000@y...> wrote:I also don't know if the
> light is the best solution to choose. Right
> > now I'm looking for some solutions to my problem. What I know is
> that
> > I send a signal (probably a light ray) into some device... the
> light
> > will be divided into some nodes of the device and because of that
> I
> > will have multiple rays at the destination. But I know the moment
> > when a particular ray will arrive there. I need only to know
> whether
> > that particular ray has arrived there (or it was stuck somewhere).
> >
> > Do you think that I could use another kind of signal (instead of
> > light). At a theoretical level I work with signals, but if I want
> to
> > make an implementation probably (???) the light is the best.
> Because
> > I need SPEED.
> >
> > Any suggestions are welcomed !
> >
> > Thanks,
> > M
> >
> > --- In Electronics_101@yahoogroups.com, One Two
<smjones1969@s...>
> > wrote:
> > >
> > > I don't know much about optical equipment, but I have made
> circuits
> > that detect light intensity. A photodiode, wired in a
> transresistive
> > mode, can be made to have incredibly high gains, allowing even
the
> > smallest of light changes to be detected. The speed at which the
> > circuit functions will be dependent on the type of op amp you
use.
> > >
> > > computer50000 <computer50000@y...> wrote:Hi there,
> > >
> > > I need a device which can measure the fluctuations, in a light
> ray,
> > > with the speed of light.
> > >
> > > I mean, I need to know if at second 10^-8 (ten to power minus
8)
> I
> > have
> > > a fluctuation in a light ray. I'm not interested to compute the
> > power
> > > of that ray. I'm just interested to know if at a given moment
in
> > time
> > > (very, very small) it was or not a fluctuation in the intensity
> of
> > that
> > > ray.
> > >
> > > Is this possible?
> > >
> > > Thanks,
> > > Michael
> > >
> > >
> > >
> > >
> > >
> > >
> > > ---------------------------------
> > > YAHOO! GROUPS LINKS
> > >
> > >
> > > Visit your group "Electronics_101" on the web.
> > >
> > > To unsubscribe from this group, send an email to:
> > > Electronics_101-unsubscribe@yahoogroups.com
> > >
> > > Your use of Yahoo! Groups is subject to the Yahoo! Terms of
> > Service.
> > >
> > >
> > > ---------------------------------
> > >
> >
> >
> >
> >
> >
> >
> >
> > ---------------------------------
> >
> >
> > Visit your group "Electronics_101" on the web.
> >
> > To unsubscribe from this group, send an email to:
> > Electronics_101-unsubscribe@yahoogroups.com
> >
> > Your use of Yahoo! Groups is subject to the Yahoo! Terms of
> Service.
> >
> >
> > ---------------------------------
> >
>
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