Wavemeter based on interferometer - Revision history

Chris: /* Oscilloscope */

2021-05-05T11:20:00Z

Oscilloscope

← Older revision		Revision as of 19:20, 5 May 2021
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	<math>\frac{1550}{701}=2.2111</math> and from fitted line we get ratio <math>\frac{4.698}{2.12}=2.2160</math>		<math>\frac{1550}{701}=2.2111</math> and from fitted line we get ratio <math>\frac{4.698}{2.12}=2.2160</math>


			'''Comment''': Whenever possible, try to specify an uncertainty of your measurement result. In this method of determining the wavelength, it would likely be the uncertainty of +/-1 in the zero transitions during a fixed periode of the test beam. Not sure how your code exactly works, but you may or may not have to consider an uncertainty of +/-1 in the reference counts as well. The latter uncertainty you could remove if you count a fixed number of reference events, and use it to control a gate window for the test counts....

	===Arduino counter===		===Arduino counter===

Chris: /* Signal Process */

2021-05-05T11:15:06Z

Signal Process

← Older revision		Revision as of 19:15, 5 May 2021
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	</gallery>		</gallery>

			'''Comment''': Congratulation, obviously it worked ;) However, the MAR amplifiers would need a resistor at the positive supply feeding in DC current for them to actually amplify the signal. Maybe you did not need it in the case here... Also, keep in mind these amplifiers are internally terminated with 50 Ohm to ground: The additional resistors with 150 Ohm at their input only lowers the total input impedance to 1/(1/50+1/150)=37.5Ohm, so you likely have a higher cutoff frequency than what you thought. But hey, it worked!

	;Components we use:		;Components we use:

Zhao: /* Future work */

2021-04-30T03:23:23Z

Future work

← Older revision		Revision as of 11:23, 30 April 2021
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	Third, It is necessary to write an interface window to make this system easier to use. This window should allow people choose max counts and average numbers.		Third, It is necessary to write an interface window to make this system easier to use. This window should allow people choose max counts and average numbers.

			Our project gives a preliminary result here. It can be improved by solving these problems.

	==History==		==History==

Zhao: /* Code */

2021-04-29T02:33:21Z

Code

← Older revision		Revision as of 10:33, 29 April 2021
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	Serial.println((counter0_ovf_result)*256+counter0);		Serial.println((counter0_ovf_result)*256+counter0);
	Serial.println((counter1_ovf_result)*65536+counter1);		Serial.println((counter1_ovf_result)*65536+counter1);
	//clear state in case ~~of repeating~~ output		//clear state in case the board repeats output
	counter0_state = false;		counter0_state = false;
	counter1_state = false;		counter1_state = false;
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	</pre>		</pre>

	Here is the jupyter notebook Python2 code for ~~get~~ result:		Here is the jupyter notebook Python2 code for getting result:
	<pre>		<pre>

Zhao: /* Future work */

2021-04-29T02:13:29Z

Future work

← Older revision		Revision as of 10:13, 29 April 2021
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	There exist several problems to be solved here.		There exist several problems to be solved here.

	First, the wavelength of our laser unknown. So we can only get a ratio and can not get an absolute value. We plan to use a 804nm laser as reference in the future because this laser is locked and we can read the wavelength from the wavemeter in our lab.		First, the wavelength of our laser is unknown. So we can only get a ratio and can not get an absolute value. We plan to use a 804nm laser as reference in the future because this laser is locked and we can read the wavelength from the wavemeter in our lab.

	Second, in the result from Arduino board, the result shows discrete distribution. The space between boxes is limited by max counts set in Arduino code. If we want to get a higher resolution, we need higher max counts, which means a longer sampling time.		Second, in the result from Arduino board, the result shows discrete distribution. The space between boxes is limited by max counts set in Arduino code. If we want to get a higher resolution, we need higher max counts, which means a longer sampling time.

Zhao: /* Future work */

2021-04-29T02:09:17Z

Future work

← Older revision		Revision as of 10:09, 29 April 2021
Line 152:		Line 152:

	==Future work==		==Future work==
	There exist several problems here.		There exist several problems to be solved here.

	First, the wavelength of our laser unknown. So we can only get a ratio and can not get an absolute value. We plan to use a 804nm laser as reference in the future because this laser is locked and we can read the wavelength from the wavemeter in our lab.		First, the wavelength of our laser unknown. So we can only get a ratio and can not get an absolute value. We plan to use a 804nm laser as reference in the future because this laser is locked and we can read the wavelength from the wavemeter in our lab.

Zhao: /* History */

2021-04-29T02:07:29Z

History

← Older revision		Revision as of 10:07, 29 April 2021
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	===Apr 26===		===Apr 26===
	Test the wavemeter today. The circuit and counter work well but the result is wrong. The problem is from 1550 reference laser. Because this signal is not stable. When the signal is very small, the counter will miss counts. Then the counts for 1550 will be smaller than the actual number which means our result will be smaller than the real value. So need to check our setup.		Test the wavemeter today. The circuit and counter work well but the result is wrong. The problem is from 1550 reference laser. Because this signal is not stable. When the signal is very small, the counter will miss counts. Then the counts for 1550 will be smaller than the actual number which means our result will be smaller than the real value. So need to check our setup.
			===Apr 28===
			Check the setup and set smaller max counts. Now the board can work well.

	==Reference==		==Reference==

Zhao: /* Future work */

2021-04-28T14:03:52Z

Future work

← Older revision		Revision as of 22:03, 28 April 2021
Line 152:		Line 152:

	==Future work==		==Future work==
			There exist several problems here.

			First, the wavelength of our laser unknown. So we can only get a ratio and can not get an absolute value. We plan to use a 804nm laser as reference in the future because this laser is locked and we can read the wavelength from the wavemeter in our lab.

			Second, in the result from Arduino board, the result shows discrete distribution. The space between boxes is limited by max counts set in Arduino code. If we want to get a higher resolution, we need higher max counts, which means a longer sampling time.

			Third, It is necessary to write an interface window to make this system easier to use. This window should allow people choose max counts and average numbers.

	==History==		==History==

Zhao: /* Oscilloscope */

2021-04-28T13:28:29Z

Oscilloscope

← Older revision		Revision as of 21:28, 28 April 2021
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	===Oscilloscope===		===Oscilloscope===
	Here we save data from an oscilloscope. Because the sampling time is much shorter than the period of car moving, we can treat the frequency of sine signal unchanged. We can fit the line and get the frequency of signal directly. Then, the ratio gives us the ratio of laser frequency.		Here we save data from an oscilloscope(the signal from detector). Because the sampling time is much shorter than the period of car moving, we can treat the frequency of sine signal unchanged. We can fit the line and get the frequency of signal directly. Then, the ratio gives us the ratio of laser frequency.
	In a 100 <math>\mu s</math> time duration, two beat signals are sine fitted and the ratio of resulted frequency is the ratio of two lasers' frequency.		In a 100 <math>\mu s</math> time duration, two beat signals are sine fitted and the ratio of resulted frequency is the ratio of two lasers' frequency.
	<gallery widths=500px heights=400px>		<gallery widths=500px heights=400px>
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	<math>\frac{1550}{701}=2.2111</math> and from fitted line we get ratio <math>\frac{4.698}{2.12}=2.2160</math>		<math>\frac{1550}{701}=2.2111</math> and from fitted line we get ratio <math>\frac{4.698}{2.12}=2.2160</math>

	===Arduino counter===		===Arduino counter===
	For Arduino counter, because we do not limit the start point of counting(do not make sure two signals have the same phase), counts may be different. There is also fluctuation in counts. So we read 20000 samples and plot the histogram here.		For Arduino counter, because we do not limit the start point of counting(do not make sure two signals have the same phase), counts may be different. There is also fluctuation in counts. So we read 20000 samples and plot the histogram here.

Zhao: /* Signal */

2021-04-28T13:26:47Z

Signal

← Older revision		Revision as of 21:26, 28 April 2021
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	Here is the signal from detector directly.		Here is the signal from detector directly.
	<gallery widths=500px heights=400px>		<gallery widths=500px heights=400px>
	File:Wavemeter_signal\|thumb\|right\|800px\|Signal from wavemeter		File:Wavemeter_signal.jpg\|thumb\|right\|800px\|Signal from wavemeter
	</gallery>		</gallery>

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	<gallery widths=500px heights=400px>		<gallery widths=500px heights=400px>
	File:~~Wavemeter_signal~~\|thumb\|right\|800px\|Signal from wavemeter		File:Wavemeter_output.jpg\|thumb\|right\|800px\|Signal from wavemeter
	</gallery>		</gallery>