{"id":1009,"date":"2021-06-29T08:55:45","date_gmt":"2021-06-29T08:55:45","guid":{"rendered":"https:\/\/www.fibermall.com\/?p=1009"},"modified":"2023-12-08T03:30:26","modified_gmt":"2023-12-08T03:30:26","slug":"how-to-calculate-the-transmission-distance-of-pon","status":"publish","type":"post","link":"https:\/\/www.fibermall.com\/blog\/passive-optical-network-pon.htm","title":{"rendered":"Passive Optical Network(PON): Optical Attenuation and Distance Estimates"},"content":{"rendered":"

In the 1980s, with the rise of computer and multimedia technology, increasingly people began to own computers and also began to use the network (LAN or Internet), so data communication services began to emerge and the demand for Internet access emerged. As optical fiber came into the picture as a new communication medium, the optical communication industry chain was increasingly taking shape. By the end of the 1980s, in order to apply optical fiber to broadband access services, PON (Passive Optical Network)<\/strong> technology began to emerge.\u00a0<\/span><\/p>\n

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PON refers to the passive optical network. PON system should include an optical distribution network (ODN)<\/strong>, optical line terminal (OLT),<\/strong> and optical network unit (ONU)<\/strong>. Firstly, ODN is an FTTH (fiber to the home)<\/strong> optical network based on PON equipment, which provides an optical transmission channel between OLT and ONU. ODN does not contain any electronic components and electronic power supply. ODN is composed of passive components such as an optical splitter, so it does not need expensive active electronic equipment. A passive optical network (PON) consists of an OLT installed in the central control station and several ONUs installed in the user’s site. PON is the future development direction of the access network.<\/span><\/p>\n

\"how<\/span><\/p>\n

PON system block diagram<\/em><\/span><\/strong><\/span><\/p>\n

\u2666 Difference between dB and dBm<\/b><\/strong><\/span><\/p>\n

The attenuation of a light signal as it propagates along a fiber is an important consideration in the design of an optical communication system; the degree of attenuation plays a major role in determining the maximum transmission distance between a transmitter and a receiver or an in-line amplifier.<\/span><\/p>\n

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In communication engineering, the magnitude of power is usually expressed as a dBm value, which is a logarithmic measure and is defined as decibels relative to 1mW power level, that is, dBm represents decibels per milliwatt. It’s a dimensionless unit that actually specifies the power ratio rather than the exact power.<\/span><\/p>\n

The formula for dBm\u00a0is as follows:<\/span><\/p>\n

dBm = 10 * log(P \/ 1mW),\u00a0 \u00a0“P” represents the power in watts.<\/span><\/strong><\/span><\/p>\n

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It should be mentioned here that dBm and dB are different, dB is defined as the difference in power or signal strength between any two given points.<\/span><\/p>\n

The formula for dB is as follows:<\/span><\/p>\n

dB = 10 log (P1 \/ P2),\u00a0 “P1” is the power intensity of the first point and P2 is the power intensity of the second point.<\/span><\/strong><\/span><\/p>\n

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In summary, dBm is an absolute unit of measurement, and dB represents a relative number that indicates an increase or decrease in signal strength. DBm represents the absolute measure of signal strength at a given point (relative to 1mw). In addition, dB and dBm function differently in fiber optic networks: optical power is often measured in DBM, while optical fiber attenuation, loss, and insertion loss are expressed in dB.<\/span><\/p>\n

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\u00a0\u2666 <\/b>How to calculate the optical <\/b><\/strong>attenuation in a passive optical network(PON)?<\/b><\/strong><\/span><\/p>\n

In PON equipment, the maximum attenuation value of OLT is between 22-25dB, which means that the attenuation value cannot exceed 25 dB.<\/span><\/p>\n

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\n\n\n\n\t\n\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t
spec. of PLC Splitter<\/th>Typical Value of Insertion Loss<\/th>Maximum Deviation Range Between Ports<\/th>Testing Instrument<\/th>\n<\/tr>\n<\/thead>\n
1:2 50%-50%<\/td>3.4 dB<\/td>0.4 dB<\/td>Optical Power Meter<\/td>\n<\/tr>\n
1:2 5%-95%<\/td>11.8 dB : 0.6 dB<\/td>0.4 dB<\/td>Optical Power Meter<\/td>\n<\/tr>\n
1:2 10%-90%<\/td>10.4 dB : 0.9 dB<\/td>0.4 dB<\/td>Optical Power Meter<\/td>\n<\/tr>\n
1:2 20%-80%<\/td>7.4 dB : 1.3 dB<\/td>0.4 dB<\/td>Optical Power Meter<\/td>\n<\/tr>\n
1:2 30%-70%<\/td>5.6 dB : 1.9 dB<\/td>0.4 dB<\/td>Optical Power Meter<\/td>\n<\/tr>\n
1:2 40%-60%<\/td>4.4 dB : 2.6 dB<\/td>0.4 dB<\/td>Optical Power Meter<\/td>\n<\/tr>\n
1:4 equal division<\/td>7.2 dB<\/td>0.8 dB<\/td>Optical Power Meter<\/td>\n<\/tr>\n
1:8 equal division<\/td>10.7 dB<\/td>1.7 dB<\/td>Optical Power Meter<\/td>\n<\/tr>\n
1:16 equal division<\/td>14.8 dB<\/td>2.0 dB<\/td>Optical Power Meter<\/td>\n<\/tr>\n
1:32 equal division<\/td>17.8 dB<\/td>2.5 dB<\/td>Optical Power Meter<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/span><\/p>\n

\u00a0<\/i><\/em><\/span><\/p>\n

1:2 PLC\u00a0splitter attenuation is\u00a03.01 dB<\/span><\/p>\n

1:8 PLC\u00a0splitter attenuation is\u00a09.03 dB<\/span><\/p>\n

1:16 PLC\u00a0splitter attenuation is\u00a012.04 dB<\/span><\/p>\n

1:32 PLC\u00a0splitter attenuation is\u00a015.05 dB<\/span><\/p>\n

1:64 PLC\u00a0splitter attenuation is\u00a018.06 dB<\/span><\/p>\n

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\u00a0\u2666 <\/b>How to choose optical modules and calculate optical power<\/b><\/strong>?<\/b><\/strong><\/span><\/p>\n

The passive optical network (PON) uses different optical modules<\/a> to support different classes of ODN.<\/span><\/p>\n

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\u2460The optical modules in use for EPON are as follows:<\/span><\/strong><\/span><\/p>\n