Embodiments of the present invention disclose a method. The method includes determining, by an OLT, that an ONU goes offline, and sending to the ONU corresponding to an ONU identifier, a detection message that carries the ONU identifier, where the ONU identifier is an ONU identifier that is occupied before the ONU goes offline and that is not reassigned, and the detection message is used to instruct the ONU corresponding to the ONU identifier to report an identification code. The method also includes receiving, a response message, where the response message carries the identification code of the ONU that sends the response message. The method also includes and determining that the ONU corresponding to the identification code carried in the response message is a rogue ONU.

Some embodiments of the present application provide an optical module, including: a master control chip, a laser transmitter, and a laser receiver; the laser transmitter and the laser receiver being connected to the master control chip, respectively; where the laser receiver includes: a PIN photodiode, a trans-impedance amplifier with a transimpedance of no less than 43K ohms, a lens, and a shell; the PIN photodiode being electrically connected to the trans-impedance amplifier; the PIN photodiode, the trans-impedance amplifier and the lens being encapsulated within the shell in a manner of transistor out-line; and the lens being coated with an antireflection film.

Some embodiments of the present application provide an optical module, including: a master control chip, a laser transmitter, and a laser receiver; the laser transmitter and the laser receiver being connected to the master control chip, respectively; where the laser receiver includes: a PIN photodiode, a trans-impedance amplifier with a transimpedance of no less than 43K ohms, a lens, and a shell; the PIN photodiode being electrically connected to the trans-impedance amplifier; the PIN photodiode, the trans-impedance amplifier and the lens being encapsulated within the shell in a manner of transistor out-line; and the lens being coated with an antireflection film.

Disclosed is a transmitter that modulates a single-wavelength laser signal with multi-level amplitude modulation on each of two polarizations, with an additional multi-level inter-polarization phase modulation. In an experimental setup, four-level amplitude modulation is used on each of the two polarizations, and four-phase inter-polarization phase modulation is used. Other numbers of levels may be used, in variations of the disclosed techniques and apparatus. Also disclosed is a corresponding receiver, which includes a DSP algorithm that recovers, simultaneously, the information on the multiple intensities imprinted by the transmitter on each polarization and the information from the multi-level inter-polarization phase modulation.

Disclosed is a transmitter that modulates a single-wavelength laser signal with multi-level amplitude modulation on each of two polarizations, with an additional multi-level inter-polarization phase modulation. In an experimental setup, four-level amplitude modulation is used on each of the two polarizations, and four-phase inter-polarization phase modulation is used. Other numbers of levels may be used, in variations of the disclosed techniques and apparatus. Also disclosed is a corresponding receiver, which includes a DSP algorithm that recovers, simultaneously, the information on the multiple intensities imprinted by the transmitter on each polarization and the information from the multi-level inter-polarization phase modulation.

An optical system and method for seeding an optical transmitter includes a first optical transmitter comprising a first reflective optical amplifier and a second optical transmitter comprising a second reflective optical amplifier. The second optical transmitter is optically coupled to the first optical transmitter. The optical system also includes an optical cavity for seeding the first reflective optical amplifier with a first optical seed signal. The optical cavity is formed between the first reflective optical amplifier of the first optical transmitter and the second reflective optical amplifier of the second optical transmitter. The first reflective optical amplifier is configured to transmit a first optical signal to the second reflective optical amplifier and the second reflective optical amplifier is configured to provide the first optical seed signal by reflecting a portion of the first optical signal back to the first reflective optical amplifier.

An optical system and method for seeding an optical transmitter includes a first optical transmitter comprising a first reflective optical amplifier and a second optical transmitter comprising a second reflective optical amplifier. The second optical transmitter is optically coupled to the first optical transmitter. The optical system also includes an optical cavity for seeding the first reflective optical amplifier with a first optical seed signal. The optical cavity is formed between the first reflective optical amplifier of the first optical transmitter and the second reflective optical amplifier of the second optical transmitter. The first reflective optical amplifier is configured to transmit a first optical signal to the second reflective optical amplifier and the second reflective optical amplifier is configured to provide the first optical seed signal by reflecting a portion of the first optical signal back to the first reflective optical amplifier.

A window cleaning robot (100), a window cleaning robot system and a method for controlling the window cleaning robot are disclosed. The window cleaning robot (100) comprises a window cleaning robot body (10), a detecting module disposed on the window cleaning robot body (10) and configured to detect an environment outside the window cleaning robot body (10), and a controlling device connected to the detecting module and configured to control an action of the window cleaning robot body (10) based on a data detected by the detecting module.

A system includes an optical fiber assembly, a receiver and a telescope, the receiver being positioned at a receiving end of the optical fiber assembly, the telescope being positioned at a collecting end, the receiver being arranged to receive uplink modulated light signals collected by the telescope and travelling through the optical fiber assembly, the telescope comprising an optical concentrator having an inlet face and an outlet face with a surface area smaller than that of the inlet face, the telescope further including a gradient-index lens dispose d coaxially with respect to the optical concentrator so that an inlet face of the gradient-index lens extends opposite the outlet face of the optical concentrator, the collecting end of the optical fiber assembly opening out opposite an outlet face of the gradient-index lens.

A system includes an optical fiber assembly, a receiver and a telescope, the receiver being positioned at a receiving end of the optical fiber assembly, the telescope being positioned at a collecting end, the receiver being arranged to receive uplink modulated light signals collected by the telescope and travelling through the optical fiber assembly, the telescope comprising an optical concentrator having an inlet face and an outlet face with a surface area smaller than that of the inlet face, the telescope further including a gradient-index lens dispose d coaxially with respect to the optical concentrator so that an inlet face of the gradient-index lens extends opposite the outlet face of the optical concentrator, the collecting end of the optical fiber assembly opening out opposite an outlet face of the gradient-index lens.