AQ6370D Spectrum Analyzer: Accurate Measurements with DWDM System
With the rapid advancement of 5G networks, optical communication technology has ushered in unprecedented changes. Dense wavelength division multiplexing (DWDM) systems have become the core of modern fiber optic communication networks due to their efficient data transmission capability and spectrum utilization. However, the dense channel distribution and high-speed data transmission in DWDM systems place higher requirements on the optical spectrum analyzer (OSA). In this paper, we will explore how the AQ6370D spectrometer can play a key role in DWDM system measurements, especially in the accurate measurement of the core metric of optical signal-to-noise ratio (OSNR).
Importance and challenges of OSNR measurement
OSNR is an important parameter for measuring the performance of a DWDM system, which directly affects the transmission quality and reliability of the system. When measuring OSNR, the resolution of the spectrometer becomes the deciding factor. The choice of resolution should ensure that the power of the signal modulation band can be accurately captured to avoid the interference of neighboring channel signals, and also be able to distinguish the noise in a fine way, which poses a double challenge to the spectrometer.
Calculation of OSNR
In the process of testing WDM (including CWDM and DWDM) systems, OSNR (Optical Signal-to-Noise Ratio) is an important indicator of system performance. How does the resolution of the spectrometer affect the OSNR result? How to choose the right resolution?
According to the IEC specification, it can be obtained by the following formula:
The key to accurately calculating OSNR depends on the accuracy of the Pi (signal power) and Ni (noise power) of each channel obtained by the OSA. Bm is the resolution of the spectrometer during the measurement, and Br is the normalized noise bandwidth, usually 0.1 nm. Accurate measurement of Pi and Ni is determined by the resolution of the spectrum analyzer (hereafter referred to as OSA)!
AQ6370D Spectrometer: Precise Measurement with DWDM System
Yokogawa AQ6370D has a function designed for this test, “Dual Trace Function”, which enables AQ6370D to calculate the signal power and noise power of different resolutions separately. In order to get the accurate results of OSNR, we only need to scan two curves. As shown in the figure, the yellow curve Trace A reads the signal power and the red curve Trace B reads the noise power.
The Dual Trace function can be set in the ANALYSIS2-WDM-Parameter setting as shown below:Choosing a high-resolution, large dynamic range spectrometer is critical to accurately analyzing the OSNR of DWDM. with a maximum resolution of 0.02nm and a dynamic range of greater than 78dB, the AQ6370D can effectively and accurately measure the power of both signal and noise lamps, and in combination with the correct setup ensures that the OSNR is analyzed, making it an ideal choice for DWDM system measurements.
Warm tips:
The measurements described in this article are based on experimental systems, and the measurement conditions or test capabilities may vary according to the actual situation.
When using the above settings for actual measurements, depending on the system's dynamic chirp, chromatic dispersion, modulation format, etc., the measurement results will be different, and you need to reset the test conditions.
With the rapid advancement of 5G networks, optical communication technology has ushered in unprecedented changes. Dense wavelength division multiplexing (DWDM) systems have become the core of modern fiber optic communication networks due to their efficient data transmission capability and spectrum utilization. However, the dense channel distribution and high-speed data transmission in DWDM systems place higher requirements on the optical spectrum analyzer (OSA). In this paper, we will explore how the AQ6370D spectrometer can play a key role in DWDM system measurements, especially in the accurate measurement of the core metric of optical signal-to-noise ratio (OSNR).
Importance and challenges of OSNR measurement
OSNR is an important parameter for measuring the performance of a DWDM system, which directly affects the transmission quality and reliability of the system. When measuring OSNR, the resolution of the spectrometer becomes the deciding factor. The choice of resolution should ensure that the power of the signal modulation band can be accurately captured to avoid the interference of neighboring channel signals, and also be able to distinguish the noise in a fine way, which poses a double challenge to the spectrometer.
Calculation of OSNR
In the process of testing WDM (including CWDM and DWDM) systems, OSNR (Optical Signal-to-Noise Ratio) is an important indicator of system performance. How does the resolution of the spectrometer affect the OSNR result? How to choose the right resolution?
According to the IEC specification, it can be obtained by the following formula:
The key to accurately calculating OSNR depends on the accuracy of the Pi (signal power) and Ni (noise power) of each channel obtained by the OSA. Bm is the resolution of the spectrometer during the measurement, and Br is the normalized noise bandwidth, usually 0.1 nm. Accurate measurement of Pi and Ni is determined by the resolution of the spectrum analyzer (hereafter referred to as OSA)!
AQ6370D Spectrometer: Precise Measurement with DWDM System
Yokogawa AQ6370D has a function designed for this test, “Dual Trace Function”, which enables AQ6370D to calculate the signal power and noise power of different resolutions separately. In order to get the accurate results of OSNR, we only need to scan two curves. As shown in the figure, the yellow curve Trace A reads the signal power and the red curve Trace B reads the noise power.
The Dual Trace function can be set in the ANALYSIS2-WDM-Parameter setting as shown below:Choosing a high-resolution, large dynamic range spectrometer is critical to accurately analyzing the OSNR of DWDM. with a maximum resolution of 0.02nm and a dynamic range of greater than 78dB, the AQ6370D can effectively and accurately measure the power of both signal and noise lamps, and in combination with the correct setup ensures that the OSNR is analyzed, making it an ideal choice for DWDM system measurements.
Warm tips:
The measurements described in this article are based on experimental systems, and the measurement conditions or test capabilities may vary according to the actual situation.
When using the above settings for actual measurements, depending on the system's dynamic chirp, chromatic dispersion, modulation format, etc., the measurement results will be different, and you need to reset the test conditions.