Figure 1. The schematic diagram of 10G PON network<\/b><\/strong><\/span><\/p>\nAlong with the gradual evolution of 10G PON to 25G PON, the pulse code rate of the optical signal is continuously increased and more significantly affected by the fiber dispersion of the ODN network, as shown in Figure 2.<\/p>\n
Considering the evolution of PON technology after 10G PON, there are mainly two ways, one is single wavelength rate enhancement, baud rate from 10G to 25G\/40G, etc. Another is the use of multi-wavelength superposition, each wavelength bearing rate is 10G\/25Gb\/s, and the use of multi-wavelength superposition to 40G\/80G\/100G or higher rates. According to the engineering design for the use of C-band PON technology when the dispersion limited formula calculation: the transmission distance calculation formula when the incoming fiber power is +1dBm.<\/p>\n
![\"ODN](\"https:\/\/www.fibermall.com\/blog\/wp-content\/uploads\/2023\/04\/ODN-network-sketch.png\")
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Figure 2. ODN network sketch<\/b><\/strong><\/span><\/p>\nWhere L is the fiber link length (km), D is the fiber dispersion value, and B is the optical signal code rate. The parameters of G.652 fiber, which is commonly used in access networks, are used. The impact of the fiber link of the ODN network for high-speed PON technology (transmission distances at 10Gb\/s and 25Gb\/s rates for different wavelengths in the C-band) is obtained for the 10 Gb\/s and 25 Gb\/s rate cases using intensity modulation technology, as shown in Figure 3.<\/p>\n
![\"Impact](\"https:\/\/www.fibermall.com\/blog\/wp-content\/uploads\/2023\/04\/Impact-of-dispersion-on-the-fiber-link-of-the-ODN-network-at-10G.png\")
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![\"Impact](\"https:\/\/www.fibermall.com\/blog\/wp-content\/uploads\/2023\/04\/Impact-of-dispersion-on-the-fiber-link-of-the-ODN-network-at-25G.png\")
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Figure 3. Impact of dispersion on the fiber link of the ODN network at 10 Gb\/s and 25 Gb\/s rates<\/b><\/strong><\/span><\/p>\nBased on the results, it can be seen that dispersion at 10Gb\/s and 25Gb\/s rates with multi-wavelength overlay has a progressively significant impact on the fiber link of the ODN network. The maximum theoretical value allowed for 25Gb\/s is about 7.5km, and the maximum theoretical value allowed for 10Gb\/s is about 47km. With the increasing pulse rate of the optical signal, the cumulative dispersion of the fiber link in the ODN network has a significant impact on high-speed PON technology, especially at a 25Gb\/s rate, which is close to the conservative fiber link value calculated by the current attenuation model. Therefore, it can be preliminarily concluded that driven by the demand for higher speed, especially for WDM-PON technology, the use of better optical signal modulation techniques to resist fiber link dispersion in ODN networks will be one of the key research technologies to follow.<\/p>\n
<\/span>Summary<\/b><\/strong><\/span><\/span><\/h2>\nBy analyzing the WDM-PON transmission distance using fiber CD, the effect of fiber CD on the fiber link length in WDM-PON construction under multi-wavelength stacking conditions with different access rates is obtained. It is also clear from the analysis that fiber CD should be considered as the main limiting factor for PON without dispersion-compensated fiber at access rates greater than 10Gb\/s, and the effect of fiber residual dispersion is fully considered to meet the requirements of different wavelengths in WDM-PON. Therefore, when planning for high-speed WDM-PON, the existing ODN network should be fully evaluated in advance, such as using the content of the service area and then continuing to draw a small micro-grid area, overlay OLT<\/span><\/a> deployment room or sink box OLT equipment to the access point, and for the new ODN network should be fully considered the impact of fiber link dispersion on the subsequent high-speed PON.<\/p>\n