- #1
chisuma
- 2
- 0
- TL;DR Summary
- Can anyone explain why optical spectrum analyzer plots are in negative dB
Can anyone explain why optical spectrum analyzer plots are in negative dB
Optical spectrum analyzer related
- I
- Thread starter chisuma
- Start date
In summary, optical spectrum analyzer plots are often shown in negative dB relative to 1mW of power, which is represented as dBm. This unit is only valid for absolute power measurements. The attenuation in a fiber can be calculated by the difference in input and output power on a dB scale divided by the length of the fiber in km. It is important to check the units of the spectrum analyzer to ensure accurate measurements.
- #2
berkeman
Mentor
- 67,059
- 19,877
Welcome to PhysicsForums.chisuma said:
What optical power would correspond to 0dB?
Also, which optical spectrum analyzer are you using, and are you using it to measure attenuation in optical fiber?
- #3
chisuma
- 2
- 0
Thanks Berkeman. Appreciate your response. 0 db translates to 1 mW of power. We are using Yokogawa spectrum analyzer. We are measuring power out of the fiber. Please correct me if I am wrong - I think attenuation in the fiber can be calculated by the delta in power between free space power and power out of fiber. Regarding my question as to why there are negative values in OSA spectrum, is it a relative measurement with respect to 1mW power (0 dB).
- #4
Twigg
Science Advisor
Gold Member
- 893
- 483
Often (but not always), you'll see dB with respect to 1mW written as units of dBm instead of dB. Its only a valid unit for absolute power. If you're not sure if the dB your spectrum analyzer reports are with respect to 1mW, check if the units say "dBm". If they just say "dB", you may want to test the spectrum analyzer with a signal of known power (like a visual fault indicator, the laser pointer thingy for aligning fibers). Check the signal against a power meter and the spectrum analyzer. (Note: lots of people don't distinguish between dB and dBm so just because your y-axis doesn't say dBm doesn't mean its not with respect to 1mW.)
And yes, the attenuation is typically given as the difference in input and output power on a dB scale (not a linear scale!) divided by the length of the fiber in km.
And yes, the attenuation is typically given as the difference in input and output power on a dB scale (not a linear scale!) divided by the length of the fiber in km.
1. What is an optical spectrum analyzer?
An optical spectrum analyzer (OSA) is a scientific instrument used to measure and analyze the spectral characteristics of light. It can measure the intensity and wavelength of light in a given spectrum, and display the results in a graphical format.
2. How does an optical spectrum analyzer work?
An OSA works by using a diffraction grating or a prism to split incoming light into its component wavelengths. The light is then directed onto a detector, which measures the intensity of each wavelength. This data is then processed and displayed on a screen.
3. What are the main applications of an optical spectrum analyzer?
An OSA is commonly used in telecommunications, fiber optic communication, and optical networking to measure the performance of optical components and systems. It is also used in research and development for scientific and industrial applications.
4. What are the key features to consider when purchasing an optical spectrum analyzer?
Some important features to consider include the wavelength range and resolution, dynamic range, speed and accuracy of measurements, and the availability of additional analysis capabilities such as polarization or spectral analysis.
5. Can an optical spectrum analyzer be used for both single-mode and multi-mode fibers?
Yes, most modern OSAs are capable of measuring both single-mode and multi-mode fibers. However, the instrument may need to be calibrated differently for each type of fiber to ensure accurate measurements.
Similar threads
-
Quantum Physics
-
Quantum Physics
-
New Member Introductions
-
Quantum Physics
-
New Member Introductions
-
Atomic and Condensed Matter
-
Quantum Physics
-
Quantum Physics