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FAQ about Wavelength Swept Light Source

The following is a list of frequently asked questions (FAQ) about our Wavelength Swept Light Source.

Configuration

Question

What is the difference between a bench-top type and a built-in type?

Answer

The built-in type is designed to be suitable for installation by removing the enclosure, cooling fan, connector ports, or other components from the bench-top type.
When using the built-in type, always provide air cooling matching the installation environment.

Question

How is the wavelength swept?

Answer

Our wavelength swept light sources use an external resonator design with a Rittman-Metcalf configuration.

Please refer to the Technical Note to learn more about how sweeping works.

Question

Does wavelength sweeping have an ON/OFF function and is it possible to stop the sweep at some wavelength?

Answer

Our wavelength swept light sources use the resonance motion of scanning mirror for always-on wavelength sweeping. Consequently, it is not possible to stop sweeping at a specific wavelength.

Question

What can we use the wavelength swept light source etalon signal for?

Answer

The etalon signal can be used as a reference signal for calculating the optical output wavelength.

Question

What can we use the wavelength swept light source trigger signal for?

Answer

The trigger signal can be used to synchronize the captured data timing at the customer's test equipment. The trigger position can be set for any wavelength matching the wavelength sweep timing.

Question

What can we use the wavelength swept light source USB port for?

Answer

The wavelength sweep width and the position of the trigger signal corresponding to the wavelength can be set by connecting the light source USB port to the USB port of a PC running dedicated control software. It can also be used to monitor the normal/abnormal status of the light source.

Wavelength sweep Performance

Question

What is the degree of individual difference in sweep frequency?

Answer

Due to the manufacturing accuracy of the scanning mirror used by the light source, the sweep frequency has an individual difference of 1250 ±50 Hz for the AQA5500P/AQA5500D and 150 ±20 Hz for the AQB5500P/AQB5500D.

Question

Does the sweep frequency change over time?

Answer

The sweep frequency is stable and does not change over time because our swept wavelength light sources perform frequency sweeping using the resonance motion of scanning mirror.

Question

Can the wavelength sweep range be widened?

Answer

The maximum wavelength sweep width is 110 nm for the AQA5500P/AQA5500D and 70 nm for AQB5500P/AQB5500D in the current product line and cannot be increased. Please consult us if you require a wider wavelength range.

Question

Instead of a sine-wave can the wavelength sweep be changed to a sawtooth or triangular shape?

Answer

Our wavelength swept light sources use a continuously rotating scanning mirror to sweep the frequency as a sine wave. Consequently, scanning cannot be changed to sawtooth or triangular shapes.

Question

Is it possible to increase the sweep frequency?

Answer

The sweep frequency cannot be changed because it depends on the scanning mirror fixed amplitude. However, since the wavelength sweep during one cycle changes from the short wavelength to long wavelength and back to short wavelength again, it is possible to double the wavelength sweeping by using sweep in both directions. The AQA5500P/AQA5500D models have the highest sweep frequency of 1250 Hz which can be doubled to 2500 Hz by sweeping in both directions.

Please consult us about high-speed sweeping.

Question

The ADB5500P/ADB5500D models have a sweep frequency of 150 Hz but is it possible to reduce this further?

Answer

The sweep frequency cannot be changed because it depends on the scanning mirror fixed amplitude. The AQB5500P/AQB5500D models have the lowest sweep frequency of 150 Hz.

Please consult us if you have requirements for low-speed sweeping.

Question

Does the sweep center wavelength change when the wavelength sweep width is changed?

Answer

The sweep center wavelength shifts slightly according to the wavelength sweep width.
For example, in the most extreme case, the sweep center wavelength of the AQA5500P/AQA5500D models shifts by about 1 nm when the wavelength sweep width is changed from 110 nm to 30 nm.

Performance related to coherence

Question

What is the approximate optical output coherence length?

Answer

For the AQB5500P/AQB5500D models with a sweep frequency of 150 Hz, we have confirmed a coherence length of better than 100 m at optical interference tests when the wavelength sweep width is set to 25 nm. Coherence length and sweep speed are inversely proportional. For example, halving sweep width and sweep speed approximately doubles coherence length. Since coherence length can be changed greatly by these settings, there is not specified reference value for coherence length.

To learn more about coherence length, please refer to Anritsu Technical No. 25: High-Coherence Wavelength Swept Light Source.

Дополнительные ссылки

Wavelength Swept Light Source

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