Network node

Abstract

The invention provides a network node comprising: a fiber optic interface configured to receive a first optical signal, a second optical signal, and a third optical signal from one or more remote light sources, where the first optical signal, the second optical signal, and the third optical signal each have a respective wavelength within a fiber optic transmission band, the optical fiber transmission wave band is one of an O wave band, an E wave band, an S wave band, a C wave band, an L wave band and a U / XL wave band; one or more wavelength converters configured to convert wavelengths of one or more of the first optical signal, the second optical signal, and the third optical signal; and a Rydberg atom-based transmission medium configured to be excited by the first optical signal, the second optical signal, and the third optical signal after wavelength conversion of one or more of the first optical signal, the second optical signal, and the third optical signal, such that electrons of the Rydberg atom-based transmission medium are excited to a predetermined Rydberg state.

Description

Technical Field

[0001] The invention relates to a network node, a telecommunication network comprising a network node and a method of operating a network node. Background Art

[0002] There is an emerging field of devices based on Rydberg atoms, such as atomic radio detectors, atomic clocks, and atomic gravimeters. These devices based on Rydberg atoms typically utilize laser signals to excite electrons of an atomic medium (typically comprising rubidium, cesium, or strontium atoms) to a Rydberg state. For example, in an atomic radio detector based on an atomic medium of rubidium-85 atoms, a first laser signal at 780 nm can be used to excite electrons from the ground state of the rubidium atom to a first excited state, and then a second laser signal can be used to excite electrons from the first excited state to a Rydberg state. A common wavelength of the second laser signal is 480 nm, which excites electrons to a specific Rydberg state, from which a radio frequency standardized for use in cellular telecommunication protocols can be detected.

[0003] The inventors recognize that the problem with this device based on Rydberg atoms is that the optical signals at these wavelengths suffer high attenuation when transmitted by conventional optical fibers. In other words, these optical signals are outside conventional optical fiber transmission bands, such as O-band (1260-1360nm), E-band (1360-1460nm), S-band (1460-1530nm), C-band (1530-1565nm), L-band (1565-1625nm) or U / XL-band (1625-1675nm). Therefore, these optical signals are generated by a local optical signal source (i.e., integrated with the device based on Rydberg atoms) rather than by a remote optical signal source. Remote optical signal generation will require a relatively high-power light source to compensate for attenuation and ensure that the optical signal has enough power at the device based on Rydberg atoms. Therefore, remote optical signal generation is relatively expensive and unsafe.

[0004] For long-term operation, these laser signals should be stabilized at the desired wavelength. In the example, the stability of the first laser signal that excites electrons from the ground state of the rubidium-85 atom to the first excited state (which has a line width of about 6 MHz) should not deviate more than 1 MHz within the time frame of operation to ensure effective operation. This can be achieved using saturation absorption spectroscopy, but this requires expensive and dedicated equipment. Therefore, large-scale deployment of Rydberg atom-based devices (such as in wireless telecommunications networks, where each wireless device includes a Rydberg atom-based radio frequency detector) can be very expensive because each device requires locally applied saturation absorption spectroscopy to stabilize the laser signal. Summary of the invention

[0005] According to a first aspect of the present invention, a network node is provided, the network node comprising: an optical fiber interface, the optical fiber interface being configured to receive a first optical signal, a second optical signal and a third optical signal from one or more remote light sources, wherein the first optical signal, the second optical signal and the third optical signal each have a corresponding wavelength within an optical fiber transmission band, the optical fiber transmission band being one of an O band, an E band, an S band, a C band, an L band and an U / XL band; one or more wavelength converters, the one or more wavelength converters being configured to convert the wavelength of one or more of the first optical signal, the second optical signal and the third optical signal; and a Rydberg atom-based transmission medium, the Rydberg atom-based transmission medium being configured to be excited by the first optical signal, the second optical signal and the third optical signal after wavelength conversion of one or more of the first optical signal, the second optical signal and the third optical signal, so that electrons of the Rydberg atom-based transmission medium are excited to a predetermined Rydberg state.

[0006] The network node may further include a wavelength converter of the one or more wavelength converters configured to halve a wavelength of the first optical signal, the second optical signal, and / or the third optical signal.

[0007] The network node may further include a photodetector configured to detect the RF signal at the Rydberg atom-based transmission medium as a change in the first optical signal, the second optical signal and / or the third optical signal due to electrons of the Rydberg atom-based transmission medium being excited by the RF signal from the predetermined Rydberg state to a further Rydberg state.

[0008] The network node may be included in the telecommunication network, and the telecommunication network further includes one or more light sources remote from the network node, the one or more light sources being configured to generate a first optical signal, a second optical signal, and a third optical signal, and transmit the first optical signal, the second optical signal, and the third optical signal to the network node, wherein the transmitted first optical signal, the second optical signal, and the third optical signal each have a corresponding wavelength within a fiber transmission band, and the fiber transmission band is one of an O band, an E band, an S band, a C band, an L band, and a U / XL band.

[0009] The network node may be one of a plurality of network nodes, one or more light sources may be remote from each of the plurality of network nodes, and each of the plurality of network nodes may include: a corresponding optical fiber interface configured to receive the first optical signal, the second optical signal, and the third optical signal from the one or more light sources; one or more corresponding wavelength converters configured to convert the wavelength of one or more of the first optical signal, the second optical signal, and the third optical signal; and a corresponding Rydberg atom-based transmission medium configured to be excited by the first optical signal, the second optical signal, and the third optical signal after wavelength conversion of one or more of the first optical signal, the second optical signal, and the third optical signal, so that electrons of the corresponding Rydberg atom-based transmission medium are excited to corresponding predetermined Rydberg states.

[0010] The or each network node may be a Rydberg atom based radio frequency (RF) detector.

[0011] The telecommunication network may further comprise a photodetector configured to detect the RF signal at the Rydberg atom-based transmission medium as a change of the first optical signal, the second optical signal and / or the third optical signal, the change being caused by electrons of the Rydberg atom-based transmission medium being excited by the RF signal from the predetermined Rydberg state to a further Rydberg state.

[0012] The one or more optical sources may further include a wavelength stabilization module for stabilizing the wavelength of the first optical signal, the second optical signal, and / or the third optical signal.

[0013] According to a second aspect of the present invention, there is provided a method for operating a network node in a telecommunications network, the method comprising the following steps: receiving a first optical signal, a second optical signal and a third optical signal from one or more remote light sources, wherein the first optical signal, the second optical signal and the third optical signal each have a corresponding wavelength within an optical fiber transmission band, the optical fiber transmission band being one of an O band, an E band, an S band, a C band, an L band and an U / XL band; converting the wavelength of one or more of the first optical signal, the second optical signal and the third optical signal, and after the wavelength conversion of one or more of the first optical signal, the second optical signal and the third optical signal, exciting a Rydberg atom-based transmission medium by the first optical signal, the second optical signal and the third optical signal so that electrons of the Rydberg atom-based transmission medium are excited to a predetermined Rydberg state.

[0014] The method may further comprise the following steps: detecting a radio frequency RF signal at the Rydberg atom-based transmission medium as a change in the first optical signal, the second optical signal and / or the third optical signal, the change being caused by electrons of the Rydberg atom-based transmission medium being excited by the RF signal from the predetermined Rydberg state to a further Rydberg state.

[0015] According to a third aspect of the present invention, there is provided a computer program, the computer program comprising instructions for causing the network node of the first aspect of the present invention to execute the steps of the method of the second aspect of the present invention. The computer program may be stored on a computer readable carrier medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order that the present invention may be better understood, embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0017] Figure 1 is a schematic diagram of a telecommunications network;

[0018] Figure 2 Yes Description Figure 1 Energy level diagram of the excitation of a network of Rydberg atom-based RF detectors;

[0019] Figure 3 yes Figure 1 A schematic diagram of the core network nodes of the network;

[0020] Figure 4 yes Figure 1 A schematic diagram of a network of Rydberg atom-based radio frequency detectors; and

[0021] Figure 5 It shows the operation Figure 1 Flow chart of a method for a network of Rydberg atom-based radio frequency detectors. DETAILED DESCRIPTION

[0022] Figure 1 A telecommunications network 1 is shown. The telecommunications network 1 includes a core network node 100, a first Rydberg atom-based radio frequency (RF) detector 200, and a second Rydberg atom-based RF detector 300. The core network node 100 is configured to generate a first optical signal, a second optical signal, and a third optical signal (described in detail below). The first Rydberg atom-based RF detector 200 and the second Rydberg atom-based RF detector 300 are configured to receive these first optical signals, second optical signals, and third optical signals, and to excite the electrons of their respective Rydberg atoms to a predetermined Rydberg state. This Figure 2 It is shown in Figure 2 The electron of a Rydberg atom is shown to be moved from the ground state (5S 1 / 2 ) is excited to the first excited state (5P3 / 2 ) (which may be referred to as a “pump” signal) that pulls the electrons of the Rydberg atoms from their first excited state (5P 3 / 2 ) is excited to the second excited state (5D 3 / 2 ) and the second light signal (which may be referred to as the “detection” signal) that moves the electrons of the Rydberg atoms from the second excited state (5D 3 / 2 ) is excited to a third optical signal (which may be referred to as a "coupled" signal) in a predetermined Rydberg state. In this predetermined Rydberg state, the Rydberg atoms undergo electromagnetically induced transparency (EIT), making the Rydberg atoms transparent to the detection optical signal. Then, an incident radio frequency (RF) signal at the first Rydberg atom-based RF detector 200 or the second Rydberg atom-based RF detector 300 may further excite the electrons from the predetermined Rydberg state to a further Rydberg state, wherein the energy difference between the predetermined Rydberg state and the further Rydberg state matches the energy of the RF signal (determined by its frequency). This further excitation of the electrons due to the RF signal may be detected as a change in the detection optical signal, such as a change in transparency and therefore a change in power.

[0023] Therefore, by selecting the wavelengths of the pump light signal, the detection light signal and the coupling light signal, the first Rydberg atom-based RF detector 200 and the second Rydberg atom-based RF detector 300 can be used as detectors of RF signals of a specific frequency so as to promote electrons of Rydberg atoms to a predetermined Rydberg state having an energy difference with a further Rydberg state corresponding to the frequency of the RF signal.

[0024] Back to Figure 1 , the pump optical signal, the detection optical signal and the coupling optical signal generated by the core network node 100 are provided to the multiplexer 400. The multiplexed optical signal is then transmitted to the demultiplexer 600 through the optical network 500. Then, the demultiplexed pump optical signal, the detection optical signal and the coupling optical signal are separated by the optical splitter 700 and provided to each Rydberg atom-based RF detector 200, 300. The telecommunication network 1 also includes a first photodetector 800 and a second photodetector 900. The first photodetector 800 is configured to receive the detection optical signal from the first Rydberg atom-based RF detector 200, and the second photodetector 900 is configured to receive the detection optical signal from the second Rydberg atom-based RF detector 300.

[0025] exist Figure 3The core network node 100 is shown in more detail in FIG. The core network node 100 includes a first light source 101, such as an external cavity diode laser (ECDL), a distributed feedback laser (DFL) or a fiber laser. The first light source 101 generates a pump light signal with a wavelength of 1550nm and a detection light signal with a wavelength of 1560nm. This is achieved by generating an initial light signal with a range covering 1550nm and 1560nm (e.g., 1540nm to 1570nm) and passing the initial light signal through a first resonant cavity, which has a first reference at 1550nm (to generate a pump light signal at 1550nm) and a second reference at 1560nm (to generate a detection light signal at 1560nm). The first optical cavity is controllable (as described below) to compensate for any drift from these two wavelengths.

[0026] The first light source 101 transmits a pump light signal at 1550 nm in three paths - a first path of the pump light signal from the first light source 101 to the first stabilizing module 103, a second path of the pump light signal from the first light source 101 to the first second harmonic generator (SHG) 111, and a third path of the pump light signal from the first light source 101 to the optical splitter 108. Along the first path of the pump light signal from the first light source 101 to the first stabilizing module 103, the first stabilizing module 103 is used to frequency lock the pump light signal. This can be achieved using a multi-wavelength reference cavity or a comb locking system.

[0027] Along the second path of the pump light signal from the first light source 101 to the first SHG 111, the first SHG 111 converts the pump light signal from 1550 nm wavelength to 775 nm (i.e., the pump light signal is wavelength-halved, or in other words, frequency-doubled), which is equal to the wavelength required to promote the electrons of the Rydberg atoms in the first Rydberg atom-based RF detector 200 and the second Rydberg atom-based RF detector 300 from the ground state to the first excited state. The pump light signal at 775 nm is transmitted from the first SHG 111 to the first electromagnetic induced transparency (EIT) measurement module 109. The operation of the first EIT measurement module 109 is described below.

[0028] Returning to the first light source 101, the first light source 101 transmits a detection light signal at 1560 nm in three paths - a first path of the detection light signal from the first light source 101 to the first stabilization module 103, a second path of the detection light signal from the first light source 101 to the second SHG 105, and a third path of the detection light signal from the first light source 101 to the optical splitter 108. The first stabilization module 103 is used to frequency lock the detection light signal.

[0029] Along the second path of the detection light signal from the first light source 101 to the second SHG 105, the second SHG 105 converts the detection light signal from 1560 nm to 780 nm (i.e., the detection light signal is halved in wavelength, or in other words, doubled in frequency), which is equal to the wavelength required to promote the electrons of the Rydberg atoms in the first Rydberg atom-based RF detector 200 and the second Rydberg atom-based RF detector 300 from the first excited state to the second excited state. The detection light signal at 780 nm is then transmitted in two paths, a first path from the second SHG 105 to the saturation absorption module 107, and a second path from the second SHG 105 to the first EIT measurement module 109. Along the first path from the first SHG 105 to the saturation absorption module 107, the saturation absorption module 107 is configured to absorb the detection light signal at 780 nm and generate a first reference signal representing the absorption of the detection light signal. The stabilization module 103 uses the first reference signal in a feedback control mechanism to control the first resonant cavity to maximize the amount of the detection light signal absorbed by the saturation absorption module 107. Therefore, the saturation absorption module 107, the stabilization module 103 and the first resonant cavity cooperate to stabilize the detection light source at 1560 nm, doubling the wavelength required to promote the electrons of the Rydberg atoms in the first Rydberg atom-based RF detector 200 and the second Rydberg atom-based RF detector 300 from the first excited state to the second excited state.

[0030] By acting on both the detection light signal at 1560 nm (received from the first light source 101 on the first path) and the first reference signal (received from the saturated absorption module 107), the first stabilization module 103 both frequency locks (for relatively short-term stability) and stabilizes (for relatively long-term stability) the detection light signal generated by the first light source 101.

[0031] As described above, the first EIT measurement module 109 receives a pump light signal of 775 nm from the first SHG 111 and a probe light signal of 780 nm from the second SHG 105. The first EIT measurement module 109 is configured to absorb the pump light signal of 775 nm and the probe light signal of 780 nm, and generate a second reference signal representing the absorption of the pump light signal. Note that this second reference signal only represents the absorption of the pump light signal, because the first light signal has been stabilized by the cooperation of the saturation absorption module 107, the stabilization module 103 and the first resonant cavity, as described above. The stabilization module 103 uses this second reference signal in a feedback control mechanism to control the first resonant cavity to maximize the amount of the pump light signal at 775 nm absorbed by the first EIT measurement module 109. Therefore, the first EIT measurement module 109, the stabilization module 103 and the first resonant cavity cooperate to stabilize the pump light source at 1550 nm, so that the wavelength required to promote the electrons of the Rydberg atoms in the first Rydberg atom-based RF detector 200 and the second Rydberg atom-based RF detector 300 from the ground state to the first excited state is doubled.

[0032] By acting on both the 1550nm pump light signal (received from the first light source 101 on the first path of the pump light signal) and the second reference signal (received from the first EIT measurement module 109), the first stabilization module 103 both frequency locks (for relatively short-term stability) and stabilizes (for relatively long-term stability) the pump light signal generated by the first light source 101.

[0033] Therefore, the spectrometer 108 receives a frequency-locked and stabilized pump light signal (at 1550 nm) on the third path of the pump light signal from the first light source 101 to the spectrometer 108, and receives a frequency-locked and stabilized detection light signal (at 1560 nm) on the third path of the detection light signal from the first light source 101 to the spectrometer 108.

[0034] The optical splitter 108 splits the pump optical signal into two paths—a first path of the pump optical signal from the optical splitter 108 to the optical fiber interface 113 and a second path of the pump optical signal from the optical splitter 108 to the third SHG 115. The optical splitter 108 also splits the probe optical signal into two paths—a first path of the probe optical signal from the optical splitter 108 to the optical fiber interface 113 and a second path of the probe optical signal from the optical splitter 108 to the fourth SHG 117. Along the second paths of the pump optical signal and the probe optical signal, the pump optical signal is wavelength-converted from 1550 nm to 775 nm by the third SHG 115 (i.e., it is wavelength-halved, or in other words, frequency-doubled) and then transmitted to the second EIT measurement module 119, while the probe optical signal is wavelength-converted from 1560 nm to 780 nm by the fourth SHG 117 (i.e., it is wavelength-halved, or in other words, frequency-doubled) and then transmitted to the second EIT measurement module 119.

[0035] The core network node 100 includes a second light source 121 (such as an ECDL, DFB or fiber laser), which is configured to generate a coupled optical signal with a wavelength of about 1250nm, which is equal to the wavelength required to promote the electrons of the Rydberg atoms in the first Rydberg atom-based RF detector 200 and the second Rydberg atom-based RF detector 300 from the second excited state to the predetermined Rydberg state. The second light source 121 includes a second resonant cavity with a reference at 1250nm. The second optical cavity is controllable (as described below) to compensate for any drift from this wavelength.

[0036] The coupled optical signal is transmitted in three paths—a first path of the coupled optical signal from the second light source 121 to the second stabilization module 123, a second path of the coupled optical signal from the second light source 121 to the second EIT measurement module 119, and a third path of the coupled optical signal from the second light source 121 to the optical fiber interface 113. Along the first path of the coupled optical signal from the second light source 121 to the second stabilization module 123, the second stabilization module 123 is configured to frequency lock the coupled optical signal. Again, this can be achieved using a multi-wavelength reference cavity or a comb locking mechanism.

[0037] Along the second path of the coupled optical signal from the second light source 121, the coupled optical signal is received at the second EIT measurement module 119. As described above, the second EIT measurement module 119 also receives the pump optical signal (from the third SHG 115) and the probe optical signal (from the fourth SHG 117). The second EIT measurement module 119 is also configured to receive an RF signal from the RF source 125, the wavelength of which is equal to the wavelength required to promote the electrons of the Rydberg atoms in the first Rydberg atom-based RF detector 200 and the second Rydberg atom-based RF detector 300 from a predetermined Rydberg state to a further Rydberg state (in other words, having the same wavelength as the RF signal to be detected at the Rydberg atom-based RF detectors 200, 300). The second EIT measurement module 119 is configured to absorb the 775nm pump optical signal, the 780nm probe optical signal, the 1250nm coupled optical signal, and the RF signal, and generate a third reference signal representing the absorption amount of the coupled optical signal. Note that the third reference signal represents only the coupled optical signal, because the pump optical signal and the probe optical signal have been stabilized by the cooperation of the saturated absorption module 107, the first EIT measurement module 109, the stabilization module 103 and the first resonant cavity as described above. The third reference signal is used by the second stabilization module 123 in the feedback control mechanism to control the second resonant cavity, thereby maximizing the absorption of the coupled optical signal by the second EIT measurement module 119. Therefore, the second EIT measurement module 119, the second stabilization module 123 and the second resonant cavity cooperate to stabilize the coupled optical signal at 1250 nm (the wavelength required to promote the electrons of the Rydberg atoms in the first Rydberg atom-based RF detector 200 and the second Rydberg atom-based RF detector 300 from the second excited state to the predetermined Rydberg state).

[0038] Along the third path of the coupled optical signal from the second light source 121, the frequency locked and stabilized coupled optical signal (at 1250 nm) is provided to the optical fiber interface 113. Therefore, the optical fiber interface 113 receives the frequency locked and stabilized pump optical signal of 1550 nm, the frequency locked and stabilized detection optical signal of 1560 nm, and the frequency locked and stabilized coupled optical signal of 1250 nm. These three optical signals are emitted to the corresponding first optical fiber, the second optical fiber, and the third optical fiber, which transmit the three optical signals to the multiplexer 400.

[0039] Back to Figure 1, the pump light signal, the detection light signal and the coupling light signal are multiplexed onto the multi-wavelength optical fiber by the multiplexer 400. As described above, the multiplexed optical signal is then transmitted to the demultiplexer 600 through the optical network 500, and the demultiplexer 600 demultiplexes the pump light signal, the detection light signal and the coupling light signal to the corresponding first optical fiber, the second optical fiber and the third optical fiber. The pump light signal is separated by the optical splitter 700 and distributed to both the first Rydberg atom-based RF detector 200 and the second Rydberg atom-based RF detector 300. The detection light signal is separated by the optical splitter 700 and distributed to both the first Rydberg atom-based RF detector 200 and the second Rydberg atom-based RF detector 300. The coupling light signal is separated by the optical splitter 700 and distributed to both the first Rydberg atom-based RF detector 200 and the second Rydberg atom-based RF detector 300.

[0040] Therefore, the first Rydberg atom-based RF detector 200 and the second Rydberg atom-based RF detector 300 both receive a pump optical signal of 1550 nm, a detection optical signal of 1560 nm, and a coupling optical signal of 1250 nm. Figure 4 The first Rydberg atom-based RF detector 200 is shown in more detail in FIG. The first Rydberg atom-based RF detector 200 includes an optical fiber interface 201, a first SHG 203, a second SHG 205, a wavelength shifter 207, and a transmission medium 209 (e.g., a glass-filled cavity of low-density rubidium-85 atoms). The optical fiber interface 201 receives a pump light signal, a probe light signal, and a coupled light signal from the optical splitter 700. The pump light signal is transmitted to the first SHG 203, which is configured to convert the pump light signal from 1550 nm to 775 nm (i.e., by halving the wavelength, or in other words, by doubling the frequency). The probe light signal is transmitted to the second SHG 205, which is configured to convert the probe light signal from 1560 nm to 780 nm (i.e., by halving the wavelength, or in other words, by doubling the frequency). The coupled light signal is transmitted to the wavelength shifter 207 (which can be, for example, an optical modulator). Then, the pump light signal, the probe light signal, and the coupled light signal are transmitted to the transmission medium 209. The probe light signal propagates in a first direction along the transmission medium 209, and the pump light signal and the coupled light signal propagate in a second direction (opposite to the first direction) along the transmission medium 209, overlapping with the probe light signal in the transmission medium 209. Therefore, the probe light signal propagates in the opposite direction to the pump light signal and the coupled light signal.

[0041] As mentioned above, the pump light signal moves the electrons of the Rydberg atoms from the ground state (5S 1 / 2 ) is excited to the first excited state (5P 3 / 2 ), the detection light signal drives the electrons of the rubidium-85 atoms from the first excited state (5P3 / 2 ) is excited to the second excited state (5D 3 / 2 ), the coupled optical signal drives the electrons of the rubidium-85 atoms from the second excited state (5D 3 / 2 ) to a predetermined Rydberg state. The incident RF signal at the transmission medium 209 may then further excite the electrons from the predetermined Rydberg state to a further Rydberg state, wherein the energy difference between the predetermined Rydberg state and the further Rydberg state matches the energy of the RF signal (determined by its frequency). This further excitation of electrons due to the RF signal may be detected as a change in the detection light signal, such as a change in power.

[0042] The detection light signal is transmitted from the transmission medium 209 to the fiber optic interface 201. The fiber optic interface 201 launches the detection light signal onto the optical fiber, and the detection light signal is transmitted to the first remote photodetector 800. The first remote photodetector 800 detects the change of the detection light signal caused by the incident RF signal at the transmission medium 209 of the first Rydberg atom-based RF detector 200.

[0043] The second Rydberg atom-based RF detector 300 functions in a similar manner to the first Rydberg atom-based RF detector 200, such that an RF signal of a specific frequency incident at the second Rydberg atom-based RF detector 300 causes a detectable change in the detection light signal. The detection light signal is transmitted from the second Rydberg atom-based RF detector 300 to the second photodetector 900, which detects the change in the detection light signal caused by the incident RF signal at the second Rydberg atom-based RF detector 300.

[0044] Therefore, the first Rydberg atom-based RF detector 200 and the second Rydberg atom-based RF detector 300 (in cooperation with their respective photodetectors 800, 900) can be used to detect an RF signal of a specific frequency by selecting the wavelengths of the pump light signal, the detection light signal and the coupling light signal so as to boost the electrons of the Rydberg atoms to a predetermined Rydberg state having an energy difference with a further Rydberg state corresponding to the frequency of the RF signal.

[0045] The wavelength shifter 207 can be used to convert the wavelength of the coupled optical signal between 1250 nm and 1510 nm so that the predetermined Rydberg state can be 10F 3 / 2 to 100F 7 / 3 states, which can then be used to detect incident RF signals between 2.2 GHz and 3.097 THz.

[0046] Thus, the telecommunications network 1 enables the distribution of stable optical signals to a plurality of Rydberg atom-based RF detectors to excite the electrons of the Rydberg atoms in each Rydberg atom-based RF detector to a predetermined Rydberg state. Each of the three optical signals is distributed between the light source and the Rydberg atom-based RF detector in one of the low-attenuation optical fiber transmission bands. In addition, the pump optical signal and the detection optical signal are converted by halving the wavelength (in other words, they are doubled in frequency). These advantages will be illustrated by comparison with the alternative network that will now be described.

[0047] The first alternative network includes a first light source that generates a 1560nm signal and a second light source that generates a 960nm signal. These optical signals are distributed to a remote RF detector based on Rydberg atoms, and the remote RF detector based on Rydberg atoms uses the corresponding wavelength halving SHG to convert the 1560nm signal into a 780nm signal and convert the 960nm signal into a 480nm signal. These 780nm signals and 480nm signals are used in a dual-wavelength excitation scheme to excite Rydberg atoms to a predetermined Rydberg state. Compared with the attenuation experienced by the three optical signals of the telecommunications network 1 (all of which are within the optical fiber transmission band), the 960nm signal of the first alternative network suffers from relatively high attenuation. Therefore, for the 960nm signal, the first alternative network will require a relatively high-power light source to compensate for this attenuation, which increases cost and is relatively unsafe. In other words, for the first optical signal, the second optical signal and the third optical signal, the telecommunications network 1 can use a relatively low-power and safer light source because they are within the low-attenuation optical fiber transmission band.

[0048] The second alternative network includes a first light source that generates a 1560nm signal and a second light source that generates a 1248nm light signal. These light signals are distributed to a remote Rydberg atom-based RF detector, and the 1560nm signal is halved in wavelength to be a 780nm signal. The 780nm signal is separated, and a portion of the 780nm signal is mixed with the 1248nm signal by four-wave mixing to generate a 480nm signal. Four-wave mixing is a relatively inefficient method of generating energy efficiency for exciting Rydberg atoms relative to the energy efficiency of halving the wavelengths of the first and second light signals. Therefore, the second alternative network will require a relatively high-power light source for these two light signals (particularly the 1248nm signal) to compensate for this energy inefficiency, which increases costs and is relatively unsafe. In other words, telecommunications network 1 can use relatively low-power and safer light sources for the first and second light signals because it uses a more energy-efficient wavelength conversion process.

[0049] Another benefit of the telecommunications network 1 is that the 1550nm and 1560nm optical signals are close enough together that they can be generated from a single light source.

[0050] Furthermore, as described above, the coupled optical signal is tuned (via a wavelength shifter) to select a predetermined Rydberg state and, therefore, the frequency of the RF signal to be detected. The coupled optical signal is in the range of 1250 nm to 1510 nm. The first alternative network and the second alternative network described above rely on dual wavelength excitation, wherein the 480 nm signal is tuned to select a predetermined Rydberg state. Another benefit of the telecommunications network 1 is that it is relatively easy to tune the wavelength range of the coupled optical signal compared to tuning the 480 nm signal. Such tuning can be achieved using an electro-optic modulator or an acousto-optic modulator.

[0051] In addition, the telecommunications network 1 enables the distribution of stabilized optical signals from the core network nodes to multiple Rydberg atom-based RF detectors. In the prior art, each Rydberg atom-based RF detector would require its own stabilizer. However, by distributing these optical signals and implementing the stabilizer in the core network nodes before distribution, the number of stabilizers required in the network is reduced.

[0052] The skilled person will also appreciate that the Rydberg atom-based RF detector can be used to detect electromagnetic signals of different frequencies. That is, for a specific target frequency to be detected, the system can be configured so that the detection light signal changes in response to the incident electromagnetic signal at the target frequency to be detected, for example by selecting an appropriate atomic medium (e.g., rubidium, cesium, or strontium) having a Rydberg state and a further Rydberg state (the energy difference between these states matches the target frequency), and selecting the wavelength of the pump light signal, the detection light signal, and the coupled light signal corresponding to the Rydberg state, wherein when the pump light signal, the detection light signal, and the coupled light signal are transmitted between the central network node and the Rydberg atom-based RF detector, these combined light signals have a wavelength within any one of the optical fiber transmission bands.

[0053] Therefore, when transmitting between the central network node and each Rydberg atom-based RF detector, these optical signals can have a wavelength within any fiber transmission band, such as O band (1260-1360nm), E band (1360-1460nm), S band (1460-1530nm), C band (1530-1565nm), L band (1565-1625nm) or U / XL band (1625-1675nm). In addition, one or more wavelengths in these optical signals can be converted to a specific wavelength required to promote the electrons of Rydberg atoms at the Rydberg atom-based RF detector. These one or more optical signals can also be wavelength-converted (converted to the same wavelength required to promote the electrons of Rydberg atoms) at the central network node, so that the stabilization mechanism stabilizes these optical signals at the same wavelength.

[0054] The Rydberg atom-based RF detector can also be configured to detect an RF signal of a first wavelength in a first time slot and an RF signal of a second wavelength in a second time slot by configuring a pump light signal, a detection light signal and / or a coupled light signal and a wavelength shifter of the Rydberg atom-based RF detector in each time slot.

[0055] In addition, Rydberg atoms follow a ladder configuration for electronic transitions (e.g. Figure 2 That is, any configuration (e.g., λ, Vee) may be used. It is also not necessary that the transmission medium be a low-density alkali metal glass-filled cavity, as an optical cavity of an optical fiber (e.g., a hollow core fiber) may be used instead.

[0056] Those skilled in the art will also understand that the pump optical signal, the detection optical signal and the coupled optical signal can be stabilized and frequency locked by alternative mechanisms. In the above-mentioned telecommunications network 1, the coupled optical signal is frequency locked and stabilized using an RF source, which generates an RF signal at a frequency to be detected by a first Rydberg atom-based RF detector and a second Rydberg atom-based RF detector. If the Rydberg atom-based RF detector is configured to detect RF signals of different frequencies (for example, by using different wavelength shifts in the first Rydberg atom-based RF detector and the second Rydberg atom-based RF detector), the stability of the coupled optical signal depends on the stability of the wavelength shifter. The core network node 100 may include a plurality of coupled optical signal generating and stabilizing mechanisms, each of which is configured to generate a stable coupled optical signal of a specific wavelength. Then, the first Rydberg atom-based RF detector can receive a stable coupled optical signal of a first wavelength, and the second Rydberg atom-based RF detector can receive a stable coupled optical signal of a second wavelength.

[0057] It is also not necessary that the Rydberg atom based RF detector and its corresponding photodetector are located remotely from each other. Alternatively, the photodetector may be a component of the Rydberg atom based RF detector.

[0058] The skilled person will understand that it is not necessary for the telecommunications network 1 to include a plurality of Rydberg atom-based RF detectors. That is, the Rydberg atom-based RF detectors may be replaced by any other form of Rydberg atom-based device that can be excited to a predetermined Rydberg state by three optical signals. These devices may refer to a plurality of network nodes, each of which has: an optical fiber interface configured to receive a first optical signal, a second optical signal, and a third optical signal from one or more remote light sources, the first optical signal, the second optical signal, and the third optical signal each having a corresponding wavelength within the optical fiber transmission band; one or more wavelength converters, one or more wavelength converters configured to convert the wavelength of one or more of the first optical signal, the second optical signal, and the third optical signal; and a Rydberg atom-based transmission medium, the Rydberg atom-based transmission medium configured to be excited by the first optical signal, the second optical signal, and the third optical signal after the wavelength conversion of one or more of the first optical signal, the second optical signal, and the third optical signal, so that the electrons of the Rydberg atom-based transmission medium are excited to a predetermined Rydberg state. It is not necessary for the telecommunications network to include multiple such network nodes. That is, the telecommunications network can include a single network node (with an optical fiber interface, one or more wavelength converters, and a transmission medium based on Rydberg atoms) and enjoy the benefits of using one or more relatively low-power and safer light sources for pumping optical signals, detecting optical signals, and coupling optical signals as discussed above.

[0059] It is also not necessary to use lasers to generate the three optical signals. That is, any other optical transmitter or coherent optical transmitter (such as a light emitting diode) may alternatively be used. In addition, the core network node may include a single light source or any number of light sources, depending on the specific wavelength required by the Rydberg atom-based device.

[0060] Figure 5A method of operating a device based on Rydberg atoms is shown. In step S101, the device based on Rydberg atoms receives a first optical signal, a second optical signal, and a third optical signal from one or more remote light sources, wherein the first optical signal, the second optical signal, and the third optical signal each have a wavelength within the optical fiber transmission band. In step S103, one or more of the first optical signal, the second optical signal, and the third optical signal are wavelength-converted. In step S105, after wavelength-converting one or more of the first optical signal, the second optical signal, and the third optical signal, a transmission medium of the device based on Rydberg atoms is excited by the first optical signal, the second optical signal, and the third optical signal, so that electrons of the transmission medium are excited to a predetermined Rydberg state. In an optional step S107, an RF signal is detected at the transmission medium as a change in the first optical signal, the second optical signal, and / or the third optical signal caused by the electrons of the transmission medium being excited from a predetermined Rydberg state to a further Rydberg state by the RF signal.

[0061] A person skilled in the art will appreciate that any combination of features is possible within the scope of the claimed invention.

Claims

1. A network node, comprising: a fiber optic interface configured to receive a first optical signal, a second optical signal, and a third optical signal from one or more remote optical sources, wherein the first optical signal, the second optical signal, and the third optical signal each have a respective wavelength within a fiber optic transmission band, the fiber optic transmission band being one of an O-band, an E-band, an S-band, a C-band, an L-band, and a U / XL-band; one or more wavelength converters configured to convert a wavelength of one or more of the first optical signal, the second optical signal, and the third optical signal; and A Rydberg atom-based transmission medium, wherein the Rydberg atom-based transmission medium is configured to be excited by the first light signal, the second light signal, and the third light signal after wavelength conversion of one or more of the first light signal, the second light signal, and the third light signal, so that electrons of the Rydberg atom-based transmission medium are excited to a predetermined Rydberg state.

2. The network node according to claim 1, wherein: A wavelength converter of the one or more wavelength converters is configured to halve a wavelength of the first optical signal, the second optical signal, and / or the third optical signal.

3. A network node according to any one of the preceding claims, the network node being a radio frequency (RF) detector.

4. The network node according to claim 3, further comprising a photodetector configured to detect the RF signal at the Rydberg atom-based transmission medium as a change in the first optical signal, the second optical signal and / or the third optical signal, wherein The predetermined Rydberg state has an energy difference with a further Rydberg state corresponding to the frequency of the RF signal.

5. A telecommunications network, comprising: A network node according to any one of the preceding claims; as well as One or more light sources are located away from the network node, the one or more light sources are configured to generate the first optical signal, the second optical signal, and the third optical signal, and transmit the first optical signal, the second optical signal, and the third optical signal to the network node, wherein the transmitted first optical signal, the second optical signal, and the third optical signal each have a corresponding wavelength within a fiber transmission band, and the fiber transmission band is one of an O band, an E band, an S band, a C band, an L band, and a U / XL band.

6. The telecommunications network of claim 5, wherein: The network node is one of a plurality of network nodes, the one or more light sources are remote from each of the plurality of network nodes, and each of the plurality of network nodes comprises: a corresponding fiber optic interface configured to receive the first optical signal, the second optical signal, and the third optical signal from the one or more optical sources; one or more corresponding wavelength converters, the one or more corresponding wavelength converters configured to convert the wavelength of one or more of the first optical signal, the second optical signal, and the third optical signal; and A corresponding Rydberg atom-based transmission medium, wherein the corresponding Rydberg atom-based transmission medium is configured to be excited by the first light signal, the second light signal, and the third light signal after wavelength conversion of one or more of the first light signal, the second light signal, and the third light signal, so that electrons of the corresponding Rydberg atom-based transmission medium are excited to corresponding predetermined Rydberg states.

7. A telecommunications network according to claim 5 or claim 6, wherein: The or each network node is a radio frequency, RF, detector based on Rydberg atoms.

8. The telecommunication network according to claim 7, when the network node or the plurality of network nodes is the network node or the plurality of network nodes according to any one of claims 1 to 3, the telecommunication network further comprises: A photodetector configured to detect an RF signal at the Rydberg atom-based transmission medium as a change of the first optical signal, the second optical signal and / or the third optical signal, wherein the predetermined Rydberg state has an energy difference with a further Rydberg state corresponding to the frequency of the RF signal.

9. A telecommunications network according to any one of claims 5 to 8, wherein: The one or more light sources further include a wavelength stabilization module, and the wavelength stabilization module is used to stabilize the wavelength of the first optical signal, the second optical signal and / or the third optical signal.

10. A method of operating a network node in a telecommunications network, the method comprising the steps of: receiving a first optical signal, a second optical signal, and a third optical signal from one or more remote optical sources, wherein the first optical signal, the second optical signal, and the third optical signal each have a respective wavelength within a fiber transmission band, the fiber transmission band being one of an O-band, an E-band, an S-band, a C-band, an L-band, and a U / XL-band; converting the wavelength of one or more of the first optical signal, the second optical signal and the third optical signal, and After wavelength conversion of one or more of the first optical signal, the second optical signal and the third optical signal, a Rydberg atom-based transmission medium is excited by the first optical signal, the second optical signal and the third optical signal, so that electrons of the Rydberg atom-based transmission medium are excited to a predetermined Rydberg state.

11. The method according to claim 9 or claim 10, further comprising the following steps: A radio frequency (RF) signal at the Rydberg atom-based transmission medium is detected as a change in the first, second and / or third optical signal, wherein the predetermined Rydberg state has an energy difference with a further Rydberg state corresponding to the frequency of the RF signal.

12. A computer program comprising instructions for causing a network node according to any one of claims 1 to 5 to perform the steps according to any one of claims 9 to 11.

13. A computer readable carrier medium comprising a computer program according to claim 12.

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