Patent Application
20100215360
This Non-provisional application claims priority under 35 U.S.C. ยง119(a) on Patent Application No(s). 098105376 filed in Taiwan, Republic of China on Feb. 20, 2009, the entire contents of which are hereby incorporated by reference.
1. Field of Invention
The present invention relates to an optical network unit in a passive optical network system and its abnormal detecting and power monitoring method, wherein the optical network unit is able to detect if the up-transmission data packet exceeds its allocated time slot, and to calculate the average output power of the transmitted optical signal.
2. Related Art
The optical network units 11-14 up-transmit the burst mode data to the optical line terminal 16 in a time division multiplexing (TDM) manner. During data up-transmission, each of optical network units 11-14 is only assigned to transmit data within one time slot 1, 2, 3 or 4. The optical network units 11-14 transmit data packets 111, 121, 131 and 141 at the allocated time slot 1, 2, 3 and 4, respectively.
In other words, the optical network units at the user ends are connected to an optical channel of the optical line terminal at the station end in a time division multiplexing manner. During data up-transmission, the receiver of the optical line terminal at the station end receives the optical signals transmitted from different user ends. In general, the problem diagnosis of the burst mode data transmitted from the user ends is performed at the station end by utilizing expensive apparatuses to diagnose the data transmitted from each user end, and it is impossible to respectively diagnose the data transmitted from the user ends at the user ends by the expensive apparatuses. When the data packet up-transmitted from the user end exceeds the time interval of the allocated time slot, the overall operation of the communication system is endangered.
It is an object of the present invention to provide an optical network unit and its abnormal detecting method, wherein when the data packet up-transmitted by the optical network unit exceeds a time interval of an allocated time slot, the optical network unit turns off the optical transmitter, thereby preventing the abnormal signal transmitted into the optical fiber of the passive optical network system.
It is another object of the present invention to provide a power monitoring method of the optical network unit to obtain the average output power of the optical transmitter.
To achieve the above, the present invention provides an optical network unit in a passive optical network system. The optical network unit includes an optical transmitter, an optical detector and a signal measurement module. The optical transmitter transmits an optical signal to an optical line terminal of a passive optical network system. The optical detector is utilized for monitoring the emission of the optical signal and transforming the received optical signal into a current signal. Then, the current signal is transformed into a voltage signal. The signal measurement module is connected to the optical detector for filtering and sampling the voltage signal to generate a sampling signal. The average output power of the optical transmitter can be obtained by averaging the voltage values of the sampling signal.
The optical network unit further includes a controller connected to the signal measurement module. When the up-transmission data packet of the optical network unit exceeds the time interval of the allocated time slot, the voltage values of the sampling signal have several points over a threshold. Then, the optical transmitter is turned off.
To achieve the above, the present invention also provides an abnormal detecting method of an optical network unit. The abnormal detecting method of the optical network unit includes the following steps: providing an optical transmitter for up-transmitting an optical signal to an optical line terminal of a passive optical network system; providing an optical detector for monitoring the emission of the optical signal and generating a current signal; transforming the current signal into a voltage signal; filtering and sampling the voltage signal to generate a sampling signal; and turning off the optical transmitter when several sampling points of the sampling signal continuously exceeds a threshold.
To achieve the above, the present invention also discloses a power monitoring method of an optical network unit. The power monitoring method includes the following steps: providing an optical transmitter for up-transmitting an optical signal to an optical line terminal of a passive optical network system; providing an optical detector for monitoring the emission of the optical signal and generating a current signal; transforming the current signal into a voltage signal; filtering and sampling the voltage signal to generate a sampling signal; and averaging voltage values of the sampling signal to obtain the average output power of the optical transmitter.
To sum up, in the present invention, the optical detector of the optical network unit monitors the transmitted optical signal and generates the current signal. The current signal is transformed into the voltage signal. Then, the voltage signal is filtered and sampled to generate a sampling signal. The sampling is an asynchronous low speed sampling in cooperation with an asynchronous low speed clock. The voltage signal is continuously sampled not only in the allocated time slot but also in other time slots.
In the abnormal detecting method of the optical network unit, when the up-transmission data packet of the optical network unit exceeds the time interval of the allocated time slot, the voltage values of the sampling signal have several points over a threshold. Then, the optical transmitter is turned off.
In the power monitoring method of the optical network unit, after the current signal generated by the optical detector is transformed into the voltage signal, and the voltage signal is filtered and sampled to generate a sampling signal, the voltage values of the sampling signal over the lower limit are averaged to obtain an average output power of the optical signal transmitted by the optical network unit.
The present invention will become more fully understood from the subsequent detailed description and accompanying drawings, which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawing.
A passive optical network system includes a plurality of optical network units. Each optical network unit is connected to a splitter via an optical fiber, and then connected to an optical line terminal. The optical network unit up-transmits the burst mode data to the optical line terminal in a time division multiplexing (TDM) manner. During data up-transmission, each optical network unit is allocated one time slot, and only transmits data packet in the allocated time slot.
The signal measurement module 23 includes a current-to-voltage converter 231, a low pass filter 232 and an analog-to-digital converter 233. The current-to-voltage converter 231 is connected to the optical detector 212 for transforming the current signal SC to the voltage signal SV. The low pass filter 232 is connected to the current-to-voltage converter 231 for filtering the voltage signal SV and generating a smooth voltage signal SM as shown in
The optical network unit 20 further includes a controller 25 connected to the analog-to-digital converter 233. In abnormal burst mode data, when data packet up-transmitted by the optical network unit 20 exceeds the time interval of the allocated time slot, the voltage values of several sampling points exceed the threshold continuously (as shown in
The optical network unit 20 further includes an optical transmitter driving unit 27 connected to the optical transmitter 211 for receiving a control signal of the burst mode data to drive the optical transmitter 211. The optical transmitter driving unit 27 is preferably a laser diode driver.
In step S31, the optical transmitter 211 is provided for up-transmitting the optical signal to the optical line terminal of the passive optical network system.
In step S32, the optical detector 212 is provided for monitoring the emission of the optical signal and generating the current signal SC.
In step S33, the current signal SC is transformed into a voltage signal SV.
In step S34, the voltage signal SV is filtered and sampled to generate the sampling signal SS.
The current signal SC is transformed into the voltage signal SV by a current-to-voltage converter 231. In the filtering step, the voltage signal SV is filtered by a low pass filter 232 to generate a smooth voltage signal SM. In the sampling step, the smooth voltage signal SM is sampled by an analog-to-digital converter 233 to generate the sampling signal SS.
When the voltage values of several sampling points of the sampling signal SS continuously exceed the threshold, the optical transmitter 211 is turned off.
The power monitoring method of the optical network unit 20 also includes the steps S31 to S34. The sampling signal SS is also sampled by the above-mentioned method. The same description is omitted.
The power-monitoring method further includes the following step. The voltage values of the sampling signal SS are averaged to obtain the average output power of the optical transmitter 211.
In the averaging step, only the voltage values of sampling points sampled in the allocated time slot are averaged. Furthermore, only the voltage values of the sampling signal SS over a lower limit are averaged. Alternatively, only the voltage values of the sampling signal SS between a lower limit and a higher limit are averaged.
To sum up, in the present invention, the optical detector of the optical network unit monitors the transmitted optical signal and generates the current signal. The current signal is transformed into the voltage signal. Then, the voltage signal is filtered and sampled to generate a sampling signal SS. The sampling is an asynchronous low speed sampling in cooperation with an asynchronous low speed clock. The sampling signal SS is continuously sampled not only in the allocated time slot but also in other time slots.
In the abnormal detecting method of the optical network unit, when the up-transmission data packet of the optical network unit exceeds the time interval of the allocated time slot, the voltage values of the sampling signal have several points over a threshold continuously. Then, the optical transmitter is turned off.
In the power monitoring method of the optical network unit, the current signal generated by the optical detector is transformed into the voltage signal. Then, the voltage signal is filtered and sampled to generate a sampling signal. The voltage values of the sampling signal over the lower limit are averaged to obtain an average output power of the optical signal transmitted by the optical network unit.
Although the present invention has been described with reference to specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 098105376 | Feb 2009 | TW | national |
