Abstract: An apparatus includes an input receiving a modulated optical data signal having components of at least first and second polarizations, a first optical detector receiving the data signal, the first optical detector being first polarization-selective or first polarization-sensitive, passing components of the data signal having the second polarization, and outputting a first electrical signal, a second optical detector coupled to the first optical detector to receive the components of the data signal having the second polarization, and outputting a second electrical signal, and a processor applying a Kramers-Kronig process to the first and second electrical signals, and outputting the data signal using the Kramers-Kronig processed first and second electrical signals.

Abstract: An apparatus includes an input receiving a modulated optical data signal having components of at least first and second polarizations, a first optical detector receiving the data signal, the first optical detector being first polarization-selective or first polarization-sensitive, passing components of the data signal having the second polarization, and outputting a first electrical signal, a second optical detector coupled to the first optical detector to receive the components of the data signal having the second polarization, and outputting a second electrical signal, and a processor applying a Kramers-Kronig process to the first and second electrical signals, and outputting the data signal using the Kramers-Kronig processed first and second electrical signals.

Abstract: The invention presents an equalizing device, a corresponding method and an optical signal with a frame structure for enabling the method. The equalizing device includes a first 2×2 MIMO equalizer configured to perform a first equalization on the digital signal, supported by a 2×2 MIMO channel estimation of the channel based on the digital signal. Further, the device includes a second 2×2 MIMO equalizer, arranged after the first equalizer and configured to perform a second equalization on the digital signal, supported by a State of Polarization (SOP) estimation of the optical signal based on the digital signal.

Abstract: It is provided a method and a system for secure optical data transmission. The method includes the steps of providing a bi-directional optical communication link between a first and a second party; carrying out a first channel estimation with respect to the communication link by the first party; carrying out a second channel estimation with respect to the communication link by the second party; and generating a secret key using the results of the first and the second channel estimation.

Abstract: A device and a method for multiplexing and/or demultiplexing optical signals of a plurality of wavelengths. The optical signals of the various wavelengths are combined or separated in a wavelength-selective manner. To combine or separate the individual wavelengths, only one wavelength-selective filter is used, and the optical signals are routed in such a way that they repeatedly strike the wavelength-selective filter at respectively different angles. The optical signals of only one specific wavelength are coupled in or out for each angle.