An analog distributed antenna system having a set of small cells as a signal source is provided. A proposed cellular communication system includes an upper small cell unit including upper protocol processors configured to process an upper first part of a protocol stack of a small cell, a lower small cell unit including lower protocol processors configured to process a remaining second part of the protocol stack of the small cell, and a first matching switch configured to respectively match the lower protocol processors to a plurality of remote units. According to one aspect, the cellular communication system includes a common controller configured to control activation of the plurality of upper protocol processors of the upper small cell unit and the plurality of lower protocol processors of the lower small cell unit according to a required service capacity and appropriately control an operation of the first matching switch.

A hyperspectral radiometer may comprise one or more antennas, a electro-optical modulator modulating the received RF signal onto an optical carrier to generate a modulated signal having at least one sideband; a filter filtering the modulated signal to pass the sideband to a photodetector; and a photodetector producing an electrical signal from which information of the RF signal can be extracted. In some examples, the optical sideband may be spatially dispersed to provide a plurality of spatially separate optical components to the photodetector, where the spatially separate optical components having different frequencies and correspond to different frequencies of the received RF signal. In some examples, the passed sideband may be mixed with an optical beam having a frequency offset from the optical carrier to form a combined beam having at least one optical signal component having a beat frequency from which information of the RF signal can be extracted.

An optical frequency control device includes: a detection circuit to receive first light including a first frequency, receive second light including a second frequency, modulate the first light with a local oscillation signal, and detect a differential beat signal between the frequency of sideband light included in the modulated first light and the second frequency; a light source control circuit to change the second frequency by frequency-dividing the differential beat signal with a first frequency division number, by frequency-dividing a reference signal with a second frequency division number, and by outputting a phase error signal indicating a phase difference between the frequency-divided differential beat signal and the frequency-divided reference signal; and a signal processing unit to set each of the first frequency division number and the second frequency division number according to the set value of a frequency difference between the first frequency and the second frequency.

A photonic integrated circuit (PIC) provides a common architecture to feed both optical and RF phased arrays that may be used for missile guidance, mobile data links, autonomous vehicles and 5G cellular communications. A plurality of switches are monolithically fabricated on the PIC with the optical feed network to switch the optical power of the phase-modulated optical channel signals between the integrated optical antennas and the RF antennas to produce steerable optical and RF beams. The photo-detectors and RF antennas may be discrete components or integrated with the optical feed network.

Described herein are optical phased array receivers. In various embodiments, an optical phased array receiver includes a set of antennas, each antenna configured to receive an optical signal; a local oscillator configured to generate one or more optical carrier signals; one or more optical signal combiners coupled to the set of antennas and the local oscillator, the one or more optical signal combiners configured to combine (i) the optical signals received by the antennas and (ii) the optical carrier signal; and one or more photodetectors configured to extract information carried by one or more of the received optical signals into an electrical signal, wherein the extracted information is indicative of a phase and an amplitude of the one or more of the received optical signals.

An apparatus includes an optical phased array having multiple array elements. Each array element includes an antenna element configured to transmit or receive an optical signal. Each array element also includes an electro-optic (EO) modulator associated with the antenna element, where the EO modulator is configured to modulate the optical signal transmitted or received by the antenna element. The antenna elements may be configured to transmit optical signals, the EO modulator of each array element may be configured to perform at least one of amplitude modulation and phase modulation, where at least one of the amplitude modulations and the phase modulation is based on encoded data. The antenna elements may be configured to receive optical signals, the EO modulator of each array element may be configured to perform at least one of phase modulation and amplitude modulation, and a decoder may be configured to recover data.

A photonic-based microwave generator includes a mode-locked laser that generates an optical pulse train, a feedback photodiode that samples the optical pulse train, and a servo amplifier that processes the photodiode output into a servo signal. The servo signal controls the mode-locked laser to suppress relative intensity noise on the optical pulse train. The microwave generator may also include a microwave photodiode for converting the optical pulse train into a microwave signal. The microwave generator may also include a second servo amplifier that processes a low-frequency output of the microwave photodiode into a second servo signal that drives an optical modulator that modulates the optical pulse train. The microwave photodiode, optical modulator, and servo amplifier form a feedback loop that suppresses amplitude noise on the microwave signal. By reducing amplitude noise and relative intensity noise, phase noise caused by amplitude-to-phase noise conversion is minimized.

An apparatus includes a first antenna, a tunable optical carrier source, a second antenna, and a delay generation module coupled to the first antenna and the tunable optical carrier source. The apparatus also includes a fixed wavelength optical carrier source, an optical carrier generation module coupled to the fixed wavelength optical carrier source, and a local oscillator generation module. The apparatus further includes a correlative kernel generation and integration module coupled to the delay generation module and the local oscillator generation module and an optoelectronic conversion module coupled to the correlative kernel generation and integration module.

An apparatus for generating a time-delayed product of two independent signals includes a fixed-wavelength laser. A first optical modulator is optically coupled to the fixed-wavelength laser and configured to modulate a fixed wavelength optical carrier with a first input signal of a set of input signals. The apparatus also includes a tunable laser. A second optical modulator is optically coupled to the tunable laser and configured to modulate a tunable optical carrier with a second input signal of the set of input signals. The apparatus also includes a dispersive element coupled to the second optical modulator, a first optical detector coupled to the dispersive element, a third optical modulator optically coupled to the first optical detector and the first optical modulator, an optical 90-degree hybrid element optically coupled to the third optical modulator, and a plurality of optical detectors optically coupled to the optical 90-degree hybrid element.

A system for a Rydberg atom based quantum communications transceiver is provided. The system may include a laser source for generating a photon. The system may also include one or more optical elements to create a pair of entangled photons from a generated photon, wherein the pair of entangled photons comprises a first entangled photon and a second entangled photon. The system may further include a radio-frequency (RF) based element to generate a quantum communication path from the pair of entangled photons by creating two Rydberg atom vapor cells (RAVC) that are entangled such that entangled photons may transfer or communicate their entangled state to Rydberg atoms within the Rydberg atom vapor cells (RAVCs) and form at least one entangled link with the other, the communication path comprising the least one entangled link. The system may also include one or more photon receivers, which may use at least one translation technique, to translate entangled state of each of the Rydberg atom vapor cells (RAVC).