Fiber Spectrometer

1. What are the characteristics of fiber optic spectrometer?

 

 

 

A spectral detection device that uses a fiber optic connector as the incident light interface and employs a fixed grating and array image detector for spectral separation. The spectral response range of the miniature fiber optic spectrometer is suitable for 200-2500nm.

 

 

2. What is the difference between optical resolution and pixel resolution?

 

 

 

Pixel resolution: Pixel resolution refers to the number of discrete data points in the spectral data of a spectrometer. Spectrum is usually represented in numerical form, with each data point referred to as a pixel. The higher the pixel resolution, the more data points there are in the spectrum, allowing for a more detailed observation of subtle changes in the spectrum. The pixel resolution is usually determined by the number of pixels in the detector of the spectrometer. For example, a spectrometer with a pixel count of 2048 and a pixel resolution of (800-200)/2048=0.29nm. The smaller the pixel resolution, the smaller the data point interval, and the more data points there are, the finer the spectrum.

 

 

 

Optical resolution: Optical resolution is the ability of a spectrometer to distinguish the smallest features, usually related to the optical design and performance of the instrument.

 

The optical resolution is usually determined by the performance of the optical components of the spectrometer, such as gratings, slits, and numerical apertures. For example, the optical resolution of a spectrometer may be 0.1 nanometers, which means it can distinguish light with wavelengths separated by 0.1 nanometers.

 

 

3. What is the relationship between optical resolution and diffraction limit?

 

 

 

The diffraction limit refers to the minimum distinguishable distance between two nearest points or objects in an optical system caused by diffraction effects. Optical resolution refers to the ability of an optical system to distinguish between two approaching objects or points.

 

The optical resolution is limited by the diffraction limit. Optical systems may not reach the ideal diffraction limit due to various factors, such as manufacturing accuracy of optical components, system noise, etc. But when designing and evaluating the performance of optical systems, diffraction limits provide an important reference standard.

 

4. What is the difference between signal-to-noise ratio and dynamic range?

 

 

 

Signal to Noise Ratio (SNR): SNR refers to the ratio of signal to noise. The signal represents the spectral signal of interest to us, while noise is an unwanted external signal introduced during the measurement process, which may come from the environment, light sources, electronic devices, etc.

 

The signal-to-noise ratio reflects the accuracy and stability of the spectrometer in signal measurement. A higher signal-to-noise ratio means that the measurement results are more reliable because the signal is stronger relative to the noise.

 

Dynamic range: Dynamic range refers to the size of the signal intensity range that a spectrometer can measure. It is usually expressed in decibels (dB), which is the ratio of the maximum measurable range to the minimum measurable range of signal strength.

 

The dynamic range describes the ability of a spectrometer to process signals of different intensities. A larger dynamic range means that the spectrometer can simultaneously process signals with significantly different intensities, thereby capturing information from different intensity ranges in the spectrum more comprehensively.

 

 

 

Signal to noise ratio and dynamic range are two different but related parameters that respectively measure the spectrometer's ability to measure signal accuracy and sensitivity, as well as its adaptability in handling different signal strength ranges.

 

The signal-to-noise ratio focuses on the proportional relationship between signal and noise, while the dynamic range focuses on the range of signal strength that the spectrometer can measure.

 

5. Can the wavelength density of the output data be set by oneself?

 

 

 

You can set 'Export 1nm interpolated data' to export wavelength density as 1nm, otherwise export density as pixel resolution (band range/number of pixels)

 

 

6. Can I customize the output band range (within the working wavelength range), such as only outputting within the range of 1000~1500nm?

 

 

 

Okay, preprocessing, linear interpolation, setting interpolation start and end points

 

 

7. What is point time?

 

 

 

The integration time refers to the time it takes for the sensor to accumulate the charge generated by the incident light. The accumulated charge is proportional to the integration time, so if the incident light is weak, sufficient charge can be accumulated by extending the integration time. Note that the longer the integration time, the higher the dark output of the image sensor.

 

8. What is the frequency for wavelength calibration? How to proceed?

 

 

 

The miniature spectrometer has no moving parts, so its stability is excellent. We believe there is no need to perform wavelength calibration.

 

The wavelength accuracy can be checked using a spectral line lamp with known spectral lines. To obtain calibration data again, we recommend using a high-precision monochromator to calibrate the wavelength axis at almost uniform time intervals.

 

 

9. What type of grating is used in miniature spectrometers?

 

 

 

Transmissive or reflective grating.

 

 

10. How does gap size affect detection capability?

 

 

 

The gap size of a miniature spectrometer is mainly related to its resolution and light input. Especially in terms of width, the smaller the gap size, the higher the resolution. However, the smaller the gap, the lower the light level, resulting in a decrease in the amount of incoming light. Therefore, the setting of gap size needs to consider these factors.

 

 

11. What is the wavelength reproducibility of a miniature spectrometer?

 

 

 

Due to the absence of mechanical components, the optical accuracy of the miniature spectrometer can be maintained well, resulting in high wavelength reproducibility of approximately+-0.2nm.

 

The optical structure of the miniature spectrometer is compact and robust, minimizing the influence of temperature on wavelength to 0.1 pixel/° C.

 

 

12. Can spectral resolution be improved by adjusting the slit?

 

 

 

The images of a certain wavelength on Entranceslit and CCD are mutually related, so the narrower the slit, the theoretically higher the spectral resolution of the spectrometer. Reducing the slit width can improve resolution, but it will decrease output.

 

 

13. What is the impact of slit height on the resolution of a miniature spectrometer?

 

 

 

The height of the slit theoretically does not affect the signal resolution, but only improves the signal. However, due to distortion, the slit on the CCD appears as a curve, which reduces the resolution of the spectrometer. It may also introduce some stray light.

 

 

14. What are the considerations for fiber selection in miniature spectrometers?

 

 

 

Generally, the matching of fiber wavelength range, numerical aperture NA, and core diameter size should be considered.