Photonic rf signal generation apparatus, network units and method

Patent metadata

Field	Value
Publication number	US-2024235682-A1
Application number	US-202218562036-A
Country	US
Kind code	A1
Filing date	May 11, 2022
Priority date	May 19, 2021
Publication date	Jul 11, 2024
Grant date	—

Abstract

A photonic radio frequency, RF, signal generation apparatus has a source to output a coherent optical signal at a carrier frequency; an optical splitter to split the signal into a first and a second optical carrier signal; an RF signal generation apparatus generating an RF signal at an initial frequency; an optical modulation apparatus modulating the first and second signals at the initial frequency to generate optical harmonic signals around each signal; a first optical filter to select an nth order optical harmonic signal of a first sign, +n, of the optical harmonics around the first signal; a second optical filter to select the nth order optical harmonic signal of an opposite sign, −n, of the optical harmonics around the second signal; and a combiner to combine the selected +n and −n signals to generate an optical beat signal forming an output photonic RF signal.

First claim

1 . A photonic radio frequency, RF, signal generation apparatus comprising:
a coherent optical source operable to output a coherent optical signal at a carrier frequency, ƒ 0 ; an optical splitter arranged to split the coherent optical signal into a first optical carrier signal and a second optical carrier signal; RF signal generation apparatus configured to generate at least one RF signal (V(t)) at an initial frequency, ƒ e ; optical modulation apparatus driven by the at least one RF signal and configured to modulate the first optical carrier signal and the second optical carrier signal at the initial frequency to generate a plurality of optical harmonic signals around each optical carrier signal; a first optical filter configured to select an nth order optical harmonic signal of a first sign, +n, of the plurality of optical harmonics around the first optical carrier signal; a second optical filter configured to select the nth order optical harmonic signal of an opposite sign, −n, of the plurality of optical harmonics around the second optical carrier signal; and an optical combiner arranged to combine the selected +n optical harmonic signal with the selected −n optical harmonic signal to generate an optical beat signal forming an output photonic RF signal; and an optical delay apparatus arranged to apply a delay, z, to optical signals, the optical delay apparatus being arranged to apply the delay to the first optical carrier signal before the first optical carrier signal is modulated by the optical modulation apparatus and to apply the delay to at least the −n optical harmonic signal before the optical combiner combines the −n optical harmonic signal with the selected +n optical harmonic signal.

2 . (canceled)

3 . The photonic RF signal generation apparatus as claimed in claim 1 , wherein the optical modulation apparatus comprises a bi-directional optical modulator and wherein the apparatus further comprises:
a first optical path from the optical splitter to the optical combiner for the first optical carrier signal, the first optical path including:
a path section including the bi-directional optical modulator operable to modulate the first optical carrier signal propagating in a first direction;
the optical delay apparatus; and
the first optical filter; and
a second optical path from the optical splitter to the optical combiner for the second optical carrier signal, the second optical path including:
the path section including the bi-directional optical modulator further configured to modulate the second optical carrier signal propagating in a second, opposite direction;
the optical delay apparatus; and
the second optical filter.

4 . The photonic RF signal generation apparatus as claimed in claim 1 , wherein the optical modulation apparatus comprises a first optical modulator configured to modulate the first optical carrier signal and a second optical modulator configured to modulate the second optical carrier signal and wherein the apparatus further comprises:
a first optical path from the optical splitter to the optical combiner for the first optical carrier signal, the first optical path including the first optical modulator, the optical delay apparatus and the first optical filter; and a second optical path from the optical splitter to the optical combiner for the second optical carrier signal, the second optical path including the second optical modulator, the optical delay apparatus and the second optical filter.

5 . (canceled)

6 . (canceled)

7 . The photonic RF signal generation apparatus as claimed in claim 1 , wherein the optical delay apparatus is a bi-directional delay element configured to apply the delay, τ, to optical signals, the bi-directional delay element provided within an optical path section included in the first optical path to apply the delay to the first optical carrier signal and included in the second optical path to apply the delay to at least the −n optical harmonic signal.

8 . The photonic RF signal generation apparatus as claimed in claim 7 , wherein the optical delay apparatus comprises:
a first delay element provided in the first optical path before the first optical modulator and configured to apply the delay, «, to the first optical carrier signal; and a second delay element provided in the second optical path after the second optical modulator and configured to apply the delay, τ, to at least the −n optical harmonic signal.

9 . The photonic RF signal generation apparatus as claimed in claim 8 , wherein the optical delay apparatus is a tunable optical delay apparatus.

10 . The photonic RF signal generation apparatus as claimed in claim 1 , wherein:
the RF signal generation apparatus comprises a first RF signal generator operable to generate a first RF signal (V 1 (t)) at the initial frequency, ƒ e , having a first phase, ϕ e1 (t), and a second RF signal generator operable to generate a second RF signal (V 2 (t)) at the initial frequency, ƒ e , having a second phase, ϕ e2 (t), uncorrelated to the first phase; and the optical modulation apparatus comprises a first optical modulator driven by the first RF signal (V 1 (t)) and a second optical modulator driven by the second RF signal (V 2 (t)), wherein the first optical modulator is operable to modulate the first optical carrier signal and the second optical modulator is operable to modulate the second optical carrier signal.

11 . (canceled)

12 . The photonic RF signal generation apparatus as claimed in claim 1 , wherein the first and second optical filters are tunable optical filters.

13 . The photonic RF signal generation apparatus as claimed in claim 1 , wherein the first and second optical filters are configured to select one of a first order to a tenth order optical harmonic signal of the plurality of optical harmonic signals.

14 . The photonic RF signal generation apparatus as claimed in claim 1 , wherein the initial RF frequency, ƒ e , is in the range 5-15 GHz.

15 . (canceled)

16 . The photonic RF signal generation apparatus as claimed in claim 1 , further comprising a plurality of optical splitters configured to split the optical beat signal to form a plurality of output photonic RF signals.

17 . The photonic RF signal generation apparatus as claimed in claim 16 , wherein the plurality of optical splitters are arranged in a plurality of splitting stages and wherein at least a second one of the plurality of splitting stages is followed by an amplification stage comprising a plurality of optical amplifiers arranged to amplify respective optical beat signals.

18 . The photonic RF signal generation apparatus as claimed in claim 1 , wherein the photonic RF signal generation apparatus is comprised in a communications network node.

19 .- 21 . (canceled)

22 . A radio frequency, RF, signal multiplication apparatus comprising:
a coherent optical source operable to output a coherent optical signal at a carrier frequency, ƒ 0 ; an optical splitter arranged to split the coherent optical signal into a first optical carrier signal and a second optical carrier signal; RF signal generation apparatus operable to generate at least one RF signal (V(t)) at an initial frequency, ƒ e ; optical modulation apparatus driven by the at least one RF signal and configured to modulate the first optical carrier signal and the second optical carrier signal at the initial frequency to generate a plurality of optical harmonic signals around each optical carrier signal; a first optical filter configured to sele

Assignees

• Ericsson Telefon Ab L M

Inventors

• Bigongiari Alessandra
• D'Errico Antonio
• Malacarne Antonio
• Secondini Marco
• Porzi Claudio

Classifications

• H04B10/50

  Transmitters · CPC title

• H04B10/2575 Primary

  Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier · CPC title