A bidirectional optical element in optical network units (ONUs) of a passive optical network (PON) includes a main filter configured to pass an upstream signal having an upstream-channel wavelength and a downstream signal having a downstream-channel wavelength, a drop filter configured to pass the downstream signal having the downstream-channel wavelength and reject the upstream signal having the upstream-channel wavelength, and an add filter configured to pass the upstream signal having the upstream-channel wavelength and reject the downstream signal having the downstream-channel wavelength, wherein the main filter, the drop filter, and the add filter are configured to share a single optical waveguide, and the optical waveguide is configured to connect input ports of the main filter and the drop filter and an output port of the drop filter and is provided in a straight line shape.

A multiport free-space wavelength division multiplexing (WDM) device is capable of handling multiple optical signals carried in multiple wavelengths (.sub.n) using a prism. The WDM device includes an input collimator, prism, and optical filter. The input collimator receives an optical beam containing multiple wavelengths .sub.n traveling through free-space. The prism uses at least two (2) surfaces to generate a first optical beam which travels in opposite direction of the optical beam. The optical filter is situated at a predefined angle with respect to the interface surface of the prism for facilitating frequency separation as well as extracts a first wavelength (.sub.1) from .sub.n to form a first light signal with .sub.1 and form a second optical beam with the remaining wavelengths of .sub.n. A collimator is used to guide the first light signal to a port.

Disclosed is a multi-wavelength transmission apparatus including a wavelength divider to divide an optical signal by wavelength and output wavelength-divided optical signals to different positions, the optical signal being received from an optical circulator, a first cylindrical lens to diverge the wavelength-divided optical signals along an X axis and a Y axis and allow the wavelength-divided optical signals to be promoted in a Z-direction, a second cylindrical lens to diverge optical signals output from the first cylindrical lens along the X axis and the Y axis and allow the output optical signals to be promoted in the Z-direction, and a reflector to reflect optical signals output from the second cylindrical lens toward the second cylindrical lens, the first cylindrical lens being identical in shape to the second cylindrical lens and rotated by 90 in an Y-axial direction based on the second cylindrical lens.

A wavelength division multiplexing (WDM) transceiver module comprising an optical port and an optical modulator is disclosed herein. The optical port includes a data transmit and receive optical fiber connector and a laser source-in optical fiber connector. The laser source-in optical fiber connector is configured to couple to a laser source external to the WDM transceiver module, and provide polarization alignment for a polarization-maintaining fiber. The optical modulator is configured to receive a laser output from the external laser source via the polarization-maintaining fiber and modulate the laser output based on analog electrical signals generated by a digital signal processor. The WDM transceiver module may not including an onboard laser source.

A wavelength division multiplexing (WDM) transceiver module comprising an optical port and an optical modulator is disclosed herein. The optical port includes a data transmit and receive optical fiber connector and a laser source-in optical fiber connector. The laser source-in optical fiber connector is configured to couple to a laser source external to the WDM transceiver module, and provide polarization alignment for a polarization-maintaining fiber. The optical modulator is configured to receive a laser output from the external laser source via the polarization-maintaining fiber and modulate the laser output based on analog electrical signals generated by a digital signal processor. The WDM transceiver module may not including an onboard laser source.

An optical transmission system includes: a terminal station device that transmits a wavelength multiplexed optical signal resulting from multiplexing an optical signal and dummy light; and an optical add-drop multiplexer that receives respective wavelength multiplexed optical signals transmitted from a plurality of the terminal station devices and performs add-drop processing on the wavelength multiplexed optical signals. The dummy light has a wavelength arrangement in which adjacent wavelengths are arranged with equal spacing, and the wavelength arrangement of the dummy light differs between the terminal station devices.

A system or a network may include an optoelectronic module that includes an optical transmitter optically coupled with an optical fiber, and a controller communicatively coupled to the optical transmitter. The controller may be configured to operate the optical transmitter to transmit data signals through the optical fiber. The optoelectronic module may be configured to transmit time synchronization signals through the optical fiber along with the data signals.

A transmitter (TX) for a WDM optical link includes a light source (CS) generating a plurality of discrete lines (EL) with different frequencies (f), a plurality of modulators (FSM, RRM, MZM), each modulator (FSM, RRM, MZM) being configured to modulate one of the discrete lines (EL) according to a data stream (c.sub.1-c.sub.4), at least one optical amplifier (SOA) configured to simultaneously amplify multiple lines (EL), wherein only a subset of the generated lines (EL) is routed to the optical amplifier (SOA) resp. to each one of the optical amplifiers (SOA). A receiver (RX) for an optical link adapted to work together with the transmitter (TX) is also described. An optical link including the transmitter (TX) and/or the receiver (RX), and a method to operate said link are also described.

The method includes a first encryption step of encrypting each of a plurality of data streams to obtain a respective encrypted data stream, a mapping step of mapping the plurality of encrypted data streams obtained in the first encryption step to a plurality of transmission streams for transmission via the optical transmission units, wherein the transmission streams and optical transmission units are in a one-to-one relationship, and wherein each transmission stream is mapped to by at least two of the plurality of encrypted data streams. The method further includes a second encryption step of encrypting each of the plurality of transmission streams to obtain a respective encrypted transmission stream, and a transmission step of transmitting each of the plurality of encrypted transmission streams obtained in the second encryption step via a respective optical transmission unit.

An Add Drop Multiplexer (ADM) includes a separating unit that extracts, from an ODU4 storing therein a plurality of HO-ODUs each of which stores therein at least one LO-ODU, first MSI values which correspond to the HO-ODUs and each of which identifies a different one of the LO-ODUs for each LO-ODU. The ADM includes a converting unit that converts the first MSI values which correspond to the HO-ODUs and each of which identifies a different one of the LO-ODUs, into second MSI values which correspond to the ODU4 and each of which identifies a different one of the LO-ODUs. The ADM includes an ODU processing unit that extracts the LO-ODUs from the ODU4, on the basis of the second MSI values resulting from the conversion by the converting unit.