Abstract: An optical add/drop multiplexer including one or more optical drop multiplexers connected in free space or fused by optical fiber pigtails, a wavelength blocker with an input port connected to an output port of the optical drop multiplexer through the fusion of the fiber pigtails, one or more optical add multiplexers connected in free space or fused by fiber pigtails, a digital signal processor, an analog-to-digital signal converter, a digital-to-analog converter, and a plurality of electronic control and feedback loops for tuning and scanning an optical wavelength.

Abstract: A photodiode converts an optical signal output from a laser diode to a current signal, and a current-to-voltage conversion circuit converts the current signal to a voltage signal. A comparison amplifier compares the voltage signal with a reference voltage to control the current flowing from a variable current source and increases or decreases a bias current for driving the laser diode. The current-to-voltage conversion circuit comprises a resistor and a variable current source that are connected in parallel. Therefore, it is possible to change the bias current without changing the resistance value of the resistor and to avoid limiting the dynamic range of the optical signal that is output. In addition, since the resistance value of the resistor does not change, the loop gain does not change, thereby stabilizing the control operation.

Abstract: A method of communicating data between a network device and a data network to which the device is connected via an optical fiber data link in which the device is connected to the optical fiber data link and the connection is monitored to detect data communication at a first standard. If data communication is detected at the first standard, data communication is established using the first standard. If not, the connection is monitored at the second standard. If data communication is detected at the second standard, data communication is established using the second standard.

Abstract: There is provided a method of determining transmission quality of a path in an optical communication network system obtained by connecting a plurality of networks, the method including: acquiring a value representing transmission performance corresponding to a network condition of each of spans in the path in the optical communication network system; and determining the transmission quality of the path on the basis of the acquired value representing transmission performance corresponding to the network condition of each of spans.

Abstract: A method of managing fault recovery in a trunk-branched OADM network may include determining that an optical power level over data channels of a first communications link between a first and a second terminal of the branched optical network exceeds an optical power limit. The method may further include increasing optical power sent over spare channels of the first communications link to a first level at which the optical power level over the data channels decreases to a second level below the optical power limit.

Abstract: Provided is a waveform reconstruction device capable of easily reconstructing an accurate time waveform of an optical signal without using an ultrafast time gate or a reference light source.

Abstract: An optical transceiver and methods for using the same are disclosed. The optical transceiver and methods may be useful for providing more accurate information regarding trends in operation of the optical transceiver, predicting an impending failure of the optical transceiver, and providing details of the optical transceiver prior to failure. The optical transceiver generally includes (1) at least one of (i) a receiver configured to receive optical information and (ii) a transmitter configured to transmit optical information, (2) circuitry configured to sample data for one or more operational parameters of the receiver and/or transmitter, (3) logic configured to perform one or more statistical calculations on the sampled data to generate statistical information, and (iv) one or more memories configured to store the sampled data and the statistical information.

Abstract: An apparatus comprising a receiver configured to couple to an Ethernet Passive Optical network over Coaxial (EPoC) network, and receive an upstream Orthogonal Frequency Division Multiplexing (OFDM) signal comprising a plurality of OFDM Resource Elements (REs), and a processor coupled to the receiver and configured to determine a presence of a burst marker sequence in the received signal, wherein the burst marker sequence comprises interlaced pilot symbols and null symbols, and wherein determining the presence of the burst marker sequence comprises computing a power ratio between a first set of the OFDM REs and a second set of the OFDM REs, and determining that the burst marker sequence is found when the computed power ratio exceeds a pre-determined threshold.

Abstract: An optical communication system includes an optical transmitter, and an optical receiver connected via a transmission line to the optical transmitter, in which system the optical transmitter transmits a continuous-wave light signal that enables beat detection when combined with a local oscillator signal in the optical receiver, and the optical receiver acquires a beat waveform through digital sampling by detecting the light signal using the local oscillator signal, performs frequency analysis on digitally sampled data having the beat waveform prior to demodulation, and controls the local oscillator frequency based upon the beat frequency.

Abstract: A bandwidth control method used in a case where, for example, a first communication device (OLT) allocates a bandwidth for signal transmission to each of a plurality of second communication devices (ONUs) connected to the OLT in a communication system having the OLT and the ONUs includes a sleep controlling of shifting devices among the ONUs that satisfy a predetermined condition into a power saving state, a control-target selecting of selecting control target devices among the ONUs based on a result of performing the sleep controlling, and a bandwidth determining of determining a bandwidth to be allocated to the selected control target devices.

Abstract: An optical channel monitor includes a demultiplexer, a plurality of paths and a processing section. The demultiplexer demultiplexes an input optical signal, which is wavelength-multiplexed, for respective multiplexed wavelengths to generate a plurality of optical signals. The plurality of paths respectively generate a plurality of digital signals indicating optical powers of the plurality of optical signals. The processing section inputs the plurality of digital signals to calculate correction values of the optical powers, which correspond to characteristics of the demultiplexer. The demultiplexer includes a filter having FMHM (Full With at Half Maximum) within a predetermined range. The predetermined range is set based on a pass center wavelength accuracy of the filter and an oscillation wavelength accuracy of a transponder which generates the input optical signal.

Abstract: A circuit, optical transceiver and/or methods for using the same may be useful for determining average power, extinction ratio, and/or modulation amplitude when monitoring an optical transceiver and/or optical network. The circuit generally comprises a photodiode configured to generate a first current responsive to an optical signal, a current mirror coupled to a first terminal of the photodiode, and a detector coupled to a second terminal of the photodiode. The current mirror is configured to produce a second current equal to or proportional to the first current, and the detector is configured to determine a power or amplitude of the optical signal. Further, the present scheme may communicate information using a low speed signal superimposed on or combined with the relatively high speed optical signal.

Abstract: One embodiment provides a system for performance monitoring in a passive optic network (PON). The system includes an optical line terminal (OLT) and an optical network unit (ONU). The OLT includes an optical transceiver configured to transmit optical signals to and receive optical signals from the ONU, and a performance monitoring mechanism configured to monitor performance of the PON based on received optical signals.

Abstract: An optical transmitter includes: a ring waveguide; an electrode which is formed near the ring waveguide and is provided with a signal; a first waveguide optically coupled to the ring waveguide; a second waveguide optically coupled to the ring waveguide without optically coupled directly to the first waveguide; and a light source configured to supply continuous wave light to the first waveguide.

Abstract: The present invention is directed to a method including determining an appropriate power level for a phase modulator for an optimum number of subcarriers; and applying the determined appropriate power level via a controller to produce the optimum number of subcarriers, wherein the optimum number of subcarriers enables an optical-orthogonal frequency division multiplex O-OFDM based variable rate transmitter with automatic control by a controller to produce an optimum setting based on a required rate.

Abstract: A technique for controlling power of a network node in an optical mesh network, comprising: determining a number of optical paths ingressing or expected to ingress the node, determining capacity or expected capacity of each of the paths; calculating for each of the paths a virtual input power Pvirtual, based on estimation of relative capacity of a specific path with respect to total capacity of all the paths; applying to the network node a power control mechanism, while utilizing a corresponding virtual input power Pvirtual as input power of any of the paths.

Abstract: A photonic communication system communicates M signals over a waveguide by modulating M wavelengths of light. N photonic rings at a receiver, where N is greater than M, are used to demodulate the M wavelengths. The modulated frequencies and resonant wavelengths of the receive rings are allowed to drift relative to one another. The number of receive rings is greater than the number of modulated frequency, and the number and optical characteristics of the receive rings are selected such that a subset of the receive rings effectively demodulates over the operational frequency range of the incoming light. The system tracks relative drift between the modulated wavelengths and the resonant wavelengths of the receiving rings and automatically selects the correct modulated signal or signals from among the receiving rings. The free spectral ranges and optical lengths of the receive rings are selected to reduce or minimize the number of receive rings required to span the optical bandwidth of the modulated light.

Abstract: An OCM monitors a plurality of SW ports each receiving an optical signal by switching the SW ports. The OCM includes a PD, a control circuit, and an arithmetic circuit. The PD detects an optical power level on wavelengths spaced at predetermined intervals in each of the SW ports to be monitored. The control circuit determines, in each of the SW ports, whether arithmetic processing using a waveform estimated from the optical power level is executed, depending on presence or absence of a change in the optical power level detected by the PD. The arithmetic circuit performs the arithmetic processing by using the waveform when the control circuit determines execution of the arithmetic processing.

Abstract: A circuit and a method for controlling multi-channel power are disclosed. The method includes: according to a channel selection signal in the previous clock cycle, select one channel signal from the received at least one channel signal in the previous clock cycle; according to an amplification factor control signal in the previous clock cycle, amplify the selected one channel signal to acquire a first signal; perform A/D conversion on the first signal to acquire a second signal; and according to the second signal, generate an amplification factor control signal in the next clock cycle, so that according to the amplification multiple control signal in the next clock cycle, amplify the selected one channel signal in the next clock cycle when the next clock cycle comes. The scheme can be used to detect the multi-channel optical power and its circuit implementation is simple.

Abstract: Provided is an optical network unit saving power. The optical network unit may include a processor checking whether at least one downward physical block, the upward physical block and a data switching block operate in an idle mode, sequentially transiting at least one downward physical block, an upward physical block and a data switching block to a sleep mode according to the checking result and sequentially transiting an optical transmission-reception block and the medium access control block to a sleep mode by judging whether or not a medium access control block transits to a sleep mode.

Abstract: A method for communicating optically between nodes of an optical network, including forming, between a first node and a second node of the network, a set of lightpaths, each of the set of lightpaths having a respective configuration, and transferring communication traffic between the first and second nodes via the set of lightpaths. The method also includes forming a determination for the set of lightpaths that a communication traffic level associated therewith is less than a predetermined threshold, and in response to the determination, removing a lightpath having a given configuration from the set of lightpaths to form a reduced set of lightpaths. The method further includes transferring the communication traffic between the first and second nodes via the reduced set of lightpaths, while reducing a level of power consumption in the removed lightpath and while maintaining the given configuration of the removed lightpath.

Abstract: The system and method for ameliorating the effect of close-in user equipment up to a point where the user equipment itself limits the performance. The system and method utilizes a digital filter in front of the LASER modulator being applied to the LASER. Additionally, total power detectors may be used at input to prevent unwanted signals from overloading stages in front of the LASER. In uplink and downlink directions, bidirectional digital filtering in the RUs allows the selective use of a given RU in a given sub-band, by a given WSP. The use of digital filtering in the RU reduces the need for hardware RF switching at the head end to accomplish the same objective of signal flexibility, by one of more WSPs, providing one or more sectors exists within the DAS.

Abstract: Optical network protection devices and protection methods including: a working line; a protection line; a determination module configured to determine the protection type of optical network; a first judgment module configured to judge whether the working line is normal according to performance parameter values of service signal in the working line and switching conditions configured for multiplexing section protection when the protection type of optical network is the multiplexing section protection; a second judgment module, configured to judge whether the working line is normal according to performance parameter values of service signal in the working line and switching conditions configured for channel section protection when the protection type of optical network is the channel section protection; a switching module, configured to take the service signal in the protection line as an output signal when working line is abnormal.

Abstract: The present invention discloses a method and a controller for commissioning a wave division multiplexing optical network during capacity expansion.

Abstract: A method of automatically switching connection is disclosed in the present invention. The method is applied to connection setting between a signal transmission device and at least one signal transceiver device. The method includes outputting a detecting signal to search the signal transceiver device within an effective range of the detecting signal, receiving a reacting signal generated according to the detecting signal, analyzing the detecting signal wherein the detecting signal represents a distance between the signal transmission device and the signal transceiver device, and switching the connection setting of the signal transmission device when the distance is smaller than a threshold, so that the signal transmission device can be matched with the signal transceiver device.

Abstract: An optical transmitter includes: a selection circuit; a signal processing circuit; an optical modulator; and a control circuit. The selection circuit selects signal components on the sides of the maximum and minimum values in a multivalued electrical signal for modulation of a transmitting signal. The signal processing circuit generates a multivalued electrical signal into which the transmitting signal is converted by a combination of a superimposed signal that a low-frequency wave is superimposed on the signal components and a signal having a plurality of intermediate amplitude values on which the low-frequency wave is not superimposed. The optical modulator modulates a carrier light on the basis of the multivalued electrical signal. The control circuit controls the reference amplitude value or amplitude of the multivalued electrical signal on the basis of the low-frequency components contained in a modulated optical signal.

Abstract: A method of determining a power correction factor for an optical power of an optical channel of a wavelength division multiplexed communications network. The method comprises configuring an optical source of the communications network to generate an unmodulated optical carrier signal for the optical channel. The method further comprises determining the optical power of the unmodulated optical carrier signal (PHIGH). The method further comprises configuring the optical source to apply a test modulation pattern to the optical carrier signal, to generate a modulated optical carrier signal. The method further comprises determining the optical power of the modulated optical carrier signal (PMOD). The method further comprises determining a power correction factor for the optical channel by determining the difference between the optical powers of the unmodulated optical carrier signal and the modulated optical carrier signal.

Abstract: A method and apparatus for testing an optical coupler. Inputs of the optical coupler are connected to output ports of an optical signal source. Outputs of the optical coupler are connected to input ports of an optical signal detector system. Optical signals sent through combinations of the inputs and the outputs of the optical coupler are measured using a switching system controlled by a controller to form measurements of the optical signals.

Abstract: The optical receiver includes: a photoelectric conversion circuit for receiving an optical signal and converting the received optical signal into an electrical signal; a comparator for outputting a first determination signal (S1) when a voltage corresponding to the optical signal does not reach a first threshold value (TH1) and for canceling an output of the S1 when the voltage corresponding to the optical signal exceeds a second threshold value larger than TH1 during the S1 is output; a timing extraction circuit for generating a clock signal based on a frequency and a phase of the electrical signal obtained by the converting and for outputting a second determination signal (S2) when the generated clock signal does not satisfy a predetermined condition; a unit for causing the comparator to output the S1 when the S2 is output; and detects loss of optical signal while one of the S1 and S2 is output.

Abstract: A circuit for monitoring an optical receiver or transceiver, architectures, circuits, and systems including the same, and a method for monitoring received optical power are disclosed. The receiver monitoring circuit comprises an avalanche photodiode (APD), a microprocessor, and first and second transresistance amplifiers. The microprocessor is configured to supply bias voltage to the APD. Photocurrent produced by the APD is supplied to the first and second transresistance amplifiers, and then the microprocessor captures optical power from the voltage signal of the first and second transresistance amplifiers.

Abstract: A passive optical network (PON) component comprising a power switch, a detector configured to monitor the power switch, and a processor configured to receive an interrupt from the detector and transmit a message comprising a first indicator that the PON component has powered down, and a second indicator giving a reason for the power down. A passive optical network (PON) component comprising a processor configured to implement a method comprising receiving an interrupt message from a detector, determining a reason for the interrupt, and transmitting a dying gasp message comprising an indicator of the reason for the interrupt. A method comprising transmitting an alarm message comprising an optical network terminal (ONT) manual power off indicator that indicates the ONT is shutting down because a subscriber has turned off its power switch.

Abstract: There is provided a method for determining the in-band noise in agile multichannel Dense Wavelength Division Multiplexing (DWDM) optical systems, where the interchannel noise is not representative of the in-band noise in the optical channel. The method relies on the analysis of two observations of the same input optical signal. In the two observations, the linear relationship between the optical signal contribution and the optical noise contribution (e.g. the observed OSNR) is different, which allows the discrimination of the signal and noise contributions in the input optical signal. In a first approach, the two observations are provided by polarization analysis of the input optical signal. In a second, the input optical signal is obtained using two different integration widths.

Abstract: Disclosed herein is a Passive Optical Network (PON) system and method for detecting a fault in an Optical Network terminal (ONT). The PON system for detecting a fault in an ONT includes a plurality of ONTs for outputting optical signals in time slots allocated thereto in a time division access control manner and having at least one virtual ONT. An Optical Line Terminal (OLT) receives the optical signals output from the plurality of ONTs in the time division access control manner, and then detects a faulty ONT. According to the present invention, a faulty ONT that continuously outputs signals can be detected and action can be rapidly taken against system faults when a virtual ONT is formed in a plurality of ONTs connected to an OLT and then an optical signal in the section of the virtual ONT is detected, thus providing a reliable service.

Abstract: In a communication line switching method for an optical communications system in which a station-side line terminal apparatus and user-side line terminal apparatuses are connected via a plurality of redundant physical lines, the discovery of the station-side optical line terminal registering the user-side line terminal apparatuses, wherein the registered user-side line terminal apparatuses monitoring a time stamp drift error that is generated when a difference between a time stamp included in a received signal and a local time measured by the own apparatus is larger than a value set in advance and, when the time stamp drift error occurs, shifting to a deregistered state and waiting for registration by the discovery. The station-side line terminal apparatus switches a physical line from a working physical line to a backup physical line of the physical lines.

Abstract: Optical bench structure provides a platform for integrating optical transmitters, particularly Vertical-Cavity Surface-Emitting Lasers (VCSELs), with monitor photodetectors. A substrate with photodetectors on the front side is aligned with flip-chip bonding bumps so the emission of the transmitters is aligned with the monitor photodetectors and passes through the monitor photodetectors with a portion of the transmitted light absorbed by the monitor photodetectors. The photodetectors have a thin absorption region so the percentage of light absorbed may be relatively small, providing sufficient photocurrent to monitor the transmitted power having a minimal effect on the transmitted power. Microlenses are integrated on the backside of the substrate focus, steer and/or collimate the emitted optical beams from the transmitters. The structure enables photodetectors to be integrated on the optical bench allowing the received optical power to be monitored.

Abstract: Various embodiments provide for detection of tapping of an optical signal. In one embodiment an optical fiber includes a cladding region and first and second core regions. The first core region has a first core medium having a first mode-dependent loss (MDL) figure of merit. The second core region has a second core medium having a second different MDL figure of merit. Tapping of the optical signal may be determined to occur when the MDL of the first and second optical signals differs by a predetermined threshold value.

Abstract: A method for testing an optical network is disclosed. The method includes transmitting a first optical power level on a first optical port of an optical assembly, where the optical assembly includes the first optical port, an optical cable and/or an optical waveguide, and a second optical port. The optical assembly is installed in an assembled computer and the assembled computer is in a state suitable for an end user. The method includes measuring a second optical power level at the second optical port and determining a quality level by determining if the second optical power level is below a quality threshold value. The transmitting, the measuring, and the determining occur within the assembled computer. An apparatus and computer program product also perform the functions of the method.

Abstract: Adaptive power setting techniques for optical transceivers are provided. Optical signals are received at a first optical transceiver device that are transmitted from a second optical transceiver device. A receive power of the optical signals received at the first optical transceiver device from the second optical transceiver device is determined. A characteristic of optical signals transmitted by the first optical transceiver device to the second optical transceiver device is modulated to indicate to the second optical transceiver device a disparity of the receive power with respect to a target receive power level at the first optical transceiver device. Conversely, the first optical transceiver device adjusts a power level of optical signals transmitted by the first optical transceiver device to the second optical transceiver device based on a characteristic of the optical signals received at the first optical transceiver device.

Abstract: The invention refers a method and an arrangement for in service Raman gain measurements and monitoring of a wavelength division multiplex system. By measuring the power level values of a transmitted WDM signal (WMS_TX) and an optical supervisory signal (OSS_TX) at the transmitter and the power level values of the received signals (WMS_RX; OSS_RX) the Raman gain can be calculated for the different channels.

Abstract: A controller is configured to determine a first amount of current associated with a first power level. The controller is configured further to generate a digital pulse signal based on the first amount of current, where the digital pulse signal may have a second power level and an associated duty cycle. The controller is configured further to convert the digital pulse signal into a second amount of current and output the second amount of current as a pulse signal based on the duty cycle.

Abstract: A control apparatus for controlling an optical receiver having delay paths comprises an optical variable attenuator configured to generate a variable signal and provide the variable signal to the optical receiver; a fine control voltage controller configured to generate a variable fine control voltage and input the variable fine control voltage to one path of the delay paths of the optical receiver; a photo-diode voltage monitor configured to detect a first voltage value and a second voltage value; a bit error rate (BER) checker configured to estimate a bit error rate (BER) according to a signal output from the optical receiver; and a controller configured to set a value of the variable signal and a value of the variable fine control voltage and to estimate the fine control voltage that makes the bit error rate a minimum according to the first voltage value and the second voltage value.

Abstract: An apparatus and method for automatic power adjustment of an optical network system are provided by the present invention. In the automatic power adjustment system which includes a plurality of electric-adjustable optical attenuators and a power adjustment module configured in a network management board: each OA board, i.e. optical amplification board and each service forwarding board respectively report their power relevant parameters to the power adjustment module; the power adjustment module judges whether an adjustment is required for an OA board and/or a service forwarding board after performing calculation according to the power parameters reported by each OA board and each service forwarding board, and when determining that the adjustment is required, triggers the adjustable optical attenuator on the corresponding OA board and/or the service forwarding board to perform the power adjustment.

Abstract: A monitoring apparatus for detecting uncharacteristic short-term power level changes of an optical signal transmitted through an optical fiber, said monitoring apparatus comprising a power level variance calculation unit adapted to calculate a power level variance on the basis of a long-term power level and a current power level of said optical signal and a short-term variance filter adapted to filter transient changes indicated by the calculated power level variance and to generate a trouble occurrence indication indicating an uncharacteristic short-term power level change, if the filtered power level variance exceeds a predetermined power level variance.

Abstract: A method and arrangement in an Optical Network Terminal, ONT for monitoring the state of an Optical Distribution Network, ODN, in a Passive Optical Network, PON, is provided. The ONT receives an optical signal, from an Optical Line Terminal, OLT, having optical power, Po,sat, causing a Semiconductor Optical Amplifier, SOA, comprised in the ONU, to reach a saturated state. One or more parameters are measured. The parameters relates to the power provided from a power source to the SOA during a predefined time period, where the SOA is in a saturated state during the predefined time period. Information relating to the measured parameters are provided to the OLT and thereby enabling the OLT to compare the current state of the ODN to a previously measured reference state of the ODN.

Abstract: A system and method for Service Interoperability in Ethernet Passive Optical Network (SIEPON) energy saving statistics. Energy saving statistics can be collected from a plurality of subordinate nodes in a point-to-multipoint network through a mechanism that aggregates energy saving statistics as those energy saving statistics are reported upstream. Such aggregation of energy saving statistics can be advantageous in that the aggregated energy saving information can appear uncorrelated to individual subordinate nodes. Privacy concerns are thereby addressed.

Abstract: One embodiment provides a system that tests optical performance in an Ethernet passive optical network (EPON), which includes an optical line terminal (OLT) and at least one optical network unit (ONU). The system configures an ONU with a circular queue that contains test frames for testing optical performance. The OLT then notifies the ONU to transmit test frames at a specified data rate for a specified duration. After receiving test frames at the OLT, the system measures frame loss and/or bit error rate based on the received test frames.

Abstract: In a communication line switching method for an optical communications system in which a station-side line terminal apparatus and user-side line terminal apparatuses are connected via a plurality of redundant physical lines, the discovery of the station-side optical line terminal registering the user-side line terminal apparatuses, wherein the registered user-side line terminal apparatuses monitoring a time stamp drift error that is generated when a difference between a time stamp included in a received signal and a local time measured by the own apparatus is larger than a value set in advance and, when the time stamp drift error occurs, shifting to a deregistered state and waiting for registration by the discovery. The station-side line terminal apparatus switches a physical line from a working physical line to a backup physical line of the physical lines.

Abstract: An optical receiver includes: an optical amplifier amplifying an optical signal fed thereinto according to an operating current fed thereinto, the optical signal being a wavelength-multiplexed optical signal, a demultiplexer demultiplexing an optical signal output from the optical amplifier; and an operating-current control circuit selecting a monitoring target from a plurality of wavelength signals output from the demultiplexer and controlling the operating current of the optical amplifier so that optical power of the monitoring target is controlled to be a predetermined value.

Abstract: A method for receiving optical signals and a device using the same method are provided herein. The method includes the elements of receiving an input signal which includes a signal component and an interference component, wherein the interference component is subcarrier to subcarrier intermixing interference (SSII). The input signal is first converted into a frequency domain signal. The interference component of the input signal is estimated based on a mathematical model according to at least a dynamic chirp component and a static chirp component. The interference component is then cancelled from the input signal to obtain an output signal.

Abstract: The embodiments of the present invention relate to communications technology, and disclose an optical power measurement method, an Optical Line Terminal (OLT), and an Optical Network Unit (ONU). The method includes: generating a Physical Layer Operation Administration Maintenance (PLOAM) message that includes an identifier of at least one ONU to be measured and information about a time bucket that is allocated to the ONU to be measured and is used for sending upstream optical signals; sending the PLOAM message to the multiple ONUs; receiving the upstream optical signals that are sent, in the allocated time bucket, by the ONU to be measured; and detecting the received upstream optical signals, and determining the optical power of the upstream optical signals. The present invention avoid waste of bandwidth caused in the prior art when the DBA is required to allocate bandwidth to the ONU to be measured for the purpose of detecting the optical power.