Patent Description:
The disclosure relates generally to an optical modulator, and more particularly to a redirected optical modulator output.

Cryogenic computing is a form of computing in which processing components are located within a cryogenic environment, e.g., <NUM>-<NUM>. Such a cryogenic environment allows such processing components to operate with superconducting components that include, e.g., zero-resistance wires, ultrafast Josephson junction switches, fluxoids, etc. Fiber optics are one medium for moving data to/from a cryogenic computer. Such fiber optics can provide a fast, e.g., <NUM>-<NUM> Gbps, digital communication link(s) to/from the cryogenic environment and a non-cryogenic environment, e.g., a room temperature environment (e.g. <NUM>). Moreover, for application to ultra-low power cryogenic systems, use of certain modulators is limited in that some modulators generate relatively large amount of heat that negatively impacts the cryogenic environment.

<CIT>, <CIT>, <CIT> and <CIT> describe systems comprising optical modulators situated in cryogenic systems.

The invention concerns a system according to claim <NUM>.

The invention also concerns a method according to claim <NUM>.

To eliminate typical compensation for a temperature increase associated with the unused light signal within a cryogenic computing system, an example system disclosed herein redirects this unused light signal from the cryogenic environment to the non-cryogenic environment. Thus, this redirected output signal is not dissipated into the cryogenic environment. Such an example system includes a first optical device, in a non-cryogenic environment, to receive a light signal, output the light signal, receive a first modulated light signal, and output the first modulated light signal into the non-cryogenic environment. The system further includes a second optical device, in the cryogenic environment, to receive the light signal from the first optical device, output the light signal, receive the first modulated light signal, and output the first modulated light signal. The system yet further includes an optical modulator, in the cryogenic environment, to receive the light signal from the second optical device, modulate the light signal (e.g., with a superconducting electrical signal) to produce the first modulated light signal and a second modulated light signal, output the second modulated light signal, and output the first modulated light signal to the second optical device.

Some cryogenic computing systems employ optical modulators to modulate a light signal received within their cryogenic environment from a non-cryogenic environment. During their operation to modulate light signal, these optical modulators produce an output signal of unused light. Outputting such an unused light signal within the cryogenic environment raises the temperature of the cryogenic environment. This temperature increase is compensated for with increased cooling of the cryogenic environment. This temperature increase is compounded within the addition of more optical modulators, with some cryogenic computing systems employing numerous optical modulators, e.g., as much as a hundred or more, based on the amount of data being sent to a particular cryogenic computing system. The example system utilizes two optical devices to redirect the unused light signal, e.g., the first modulated light signal, from the cryogenic environment to the non-cryogenic environment. Outputting such an unused light signal into the non-cryogenic environment prevents the unused light signal from raising a temperature of the cryogenic environment and reduces an amount of cooling used to maintain a desired temperature within the cryogenic environment. The example system eliminates the need for a second fiber at the output of the second optical device and the associated complexity (e.g., mass, connectors, jackets, space, etc.), with the example system redirecting one of the two outputs from the optical modulator of the system without affecting the optical modulator's performance. Such redirection can be implemented with an integrated optical polarization beam splitter combiner (PBSC) located on a modulator chip or an integrated optical circulator located on a modulator chip.

<FIG> illustrates an example system <NUM> (e.g., ultra-low power electro-optic cryo-logic system) to redirect unused light from a cryogenic environment <NUM> (e.g., <NUM>-<NUM>) to a non-cryogenic environment <NUM> such as a room temperature environment (e.g. <NUM>). In an example, the cryogenic environment <NUM> is separated from the non-cryogenic environment <NUM> via an insulated barrier, e.g., an insulated wall, to facilitate maintaining the temperature within the cryogenic environment <NUM>. The system <NUM> includes a first optical device <NUM> in the non-cryogenic environment <NUM>. The first optical device <NUM> is coupled to a first optical fiber <NUM>, a second optical fiber <NUM> (e.g., a polarization maintaining fiber), and a third optical fiber <NUM>. The first optical device <NUM> receives a light signal on the first optical fiber <NUM> and outputs the light signal on the second optical fiber <NUM>. The first optical device <NUM> further receives a first modulated light signal from the cryogenic environment <NUM> on the second optical fiber <NUM> and outputs the first modulated light signal into the non-cryogenic environment <NUM> on the third optical fiber <NUM>. Thus, the second optical fiber <NUM> is a bi-directional path utilized to transport the light signal into the cryogenic environment <NUM> from the non-cryogenic environment <NUM>, and the first modulated light signal into the non-cryogenic environment <NUM> from the cryogenic environment <NUM> to remove or dispose of unwanted and unused light from the cryogenic environment <NUM> into the non-cryogenic environment <NUM>.

The system <NUM> further includes a modulator module <NUM> that is comprised of a second optical device <NUM> in the cryogenic environment <NUM>. The second optical device <NUM> is coupled to the second optical fiber <NUM> via a first optical waveguide <NUM>, and is further coupled to a second optical waveguide <NUM> and a third optical waveguide <NUM>. The second optical device <NUM> receives the light signal from the first optical device <NUM> via the second optical fiber <NUM>. The second optical device <NUM> outputs the light signal on the second optical waveguide <NUM>. The second optical device <NUM> also receives the first modulated light signal via the third optical waveguide <NUM> and outputs the first modulated light signal on the second optical fiber <NUM> via the first optical waveguide <NUM>.

The modulator module <NUM> further includes an optical modulator <NUM> (e.g., a 1x2 directional coupler modulator (1x2 DCM), a silicon micro resonator (SMR), or any other optical modulator that produces an output signal that can be redirected to the non-cryogenic environment <NUM>) in the cryogenic environment <NUM>. Thus, this redirected output signal is not dissipated into the cryogenic environment <NUM>. The optical modulator <NUM> is coupled to the second optical waveguide <NUM>, a third optical waveguide <NUM>, and a fourth optical waveguide <NUM>. The optical modulator <NUM> receives the light signal from the second optical device <NUM> via the second optical waveguide <NUM>. The optical modulator <NUM> modulates this received light signal (e.g., with a superconducting electrical signal) to produce the first modulated light signal and a second modulated light signal. The optical modulator <NUM> outputs the second modulated light signal to a cryogenic device <NUM>, e.g., a cryogenic computing system, within the cryogenic environment <NUM> that is coupled to the optical modulator <NUM> via the fourth optical waveguide <NUM>. In another example, the cryogenic device <NUM> is part of a cryogenic system (not shown) that provides a communication path within the cryogenic environment <NUM> and/or conveys signals from within the cryogenic environment <NUM> to the non-cryogenic environment <NUM>. The fourth optical waveguide <NUM> is coupled to a third optical fiber <NUM> to provide a data path between the optical modulator <NUM> and the cryogenic device <NUM> for the second modulated light signal. The optical modulator <NUM> also outputs the first modulated light signal to the second optical device <NUM> via the third optical waveguide <NUM>. The optical modulator <NUM> provides two "pseudo-complimentary" optical outputs in which substantially no light is wasted into the substrate of the modulator module <NUM> and which can be read out via the fourth optical waveguide <NUM> and the third optical fiber <NUM>.

Thus, the system <NUM> redirects one of the outputs of the optical modulator <NUM>, the first modulated light signal on the third optical waveguide <NUM>, from the cryogenic environment <NUM> into the non-cryogenic environment <NUM>. In particular, the second optical device <NUM> receives the first modulated light signal and outputs the first modulated light signal on the second optical fiber <NUM> on which the first modulated light signal will pass to the non-cryogenic environment <NUM>. Thereafter, the first optical device <NUM> outputs the first modulated light signal into the non-cryogenic environment <NUM> to prevent the first modulated light signal from increasing a temperature of the cryogenic environment <NUM>. Moreover, the system <NUM> eliminates the need for a second fiber at the output of the second optical device <NUM> and the associated complexity (e.g., mass, connectors, space, etc.), with the example system <NUM> redirecting one of the two outputs from the optical modulator <NUM> of the system <NUM> without affecting performance of the optical modulator <NUM>. Furthermore, the second optical device <NUM>, the optical modulator <NUM>, and their associated waveguides <NUM>, <NUM>, <NUM>, and <NUM> are integrated onto a same substrate, resulting in a diminished loss of light as it moves between such components such that nearly all of the first modulated light signal can be redirected into the non-cryogenic environment <NUM>.

<FIG> illustrates another example system <NUM> (e.g., ultra-low power electro-optic cryo-logic system) to redirect unused light from a cryogenic environment <NUM> to a non-cryogenic environment <NUM>. The system <NUM> includes a first 1x2 directional coupler <NUM> (e.g., an on-chip integrated optical polarization beam splitter/combiner) in the non-cryogenic environment <NUM>. The first 1x2 directional coupler <NUM> is coupled to a first optical fiber <NUM>, a second optical fiber <NUM> (e.g., a polarization maintaining fiber), and a third optical fiber <NUM> (e.g., a fast axis). The first 1x2 directional coupler <NUM> receives a light signal on a slow axis of the first optical fiber <NUM> and outputs the light signal on the second optical fiber <NUM>. The second optical fiber <NUM> is a polarization-maintaining (PM) fiber and carries polarized continuous wave (CW) light along its slow (e.g., horizontal) axis. The first 1x2 directional coupler <NUM> further receives a first modulated light signal on the second optical fiber <NUM> and outputs the first modulated light signal into the non-cryogenic environment <NUM> via the third optical fiber <NUM>. Thus, the second optical fiber <NUM> is a bi-directional path utilized to transport the light signal into the cryogenic environment <NUM> from the non-cryogenic environment <NUM>, and the first modulated light signal into the non-cryogenic environment <NUM> from the cryogenic environment <NUM>, with the light signal being transported into the cryogenic environment <NUM> on a slow axis of the second optical fiber <NUM> and the first modulated light signal being transported on a fast axis of the second optical fiber <NUM>.

In an example, the first optical fiber <NUM> is a slow axis light path and the third optical fiber <NUM> is a fast axis light path. However, depending upon optical properties, e.g., a reflective index of a birefringent material (e.g., silica, fluorozirconate, fluoroaluminate, chalcogenide glasses, sapphire, polystyrene, acrylic, or any other electro-optical material) of the first optical fiber <NUM> and the third optical fiber <NUM>, in another example the first optical fiber <NUM> can be a fast axis light path and the third optical fiber <NUM> can be a slow axis light path. The second optical fiber <NUM> is both a slow axis light path and a fast axis light path, with the second optical fiber <NUM> providing the slow axis light path from the non-cryogenic environment <NUM> to the cryogenic environment <NUM> and providing the fast axis light path from the cryogenic environment <NUM> to the non-cryogenic environment <NUM>. Likewise, in another example the second optical fiber <NUM> can provide a fast axis light path from the non-cryogenic environment <NUM> to the cryogenic environment <NUM> and can provide a slow axis light path from the cryogenic environment <NUM> to the non-cryogenic environment <NUM>.

The system <NUM> further includes a modulator module <NUM> that is comprised of a second 1x2 bi-directional coupler <NUM> (e.g., an on-chip integrated optical polarization beam splitter/combiner) in the cryogenic environment <NUM>. The second 1x2 bi-directional coupler <NUM> is coupled to the second optical fiber <NUM> via a first optical waveguide <NUM>, and is further coupled to a second optical waveguide <NUM> and a fifth optical waveguide <NUM>. In an example, the second optical waveguide <NUM> is a slow axis and the fifth optical waveguide <NUM> is a fast axis polarization waveguide. In another example, the second optical waveguide <NUM> is a slow axis and the fifth optical waveguide <NUM> is a slow axis polarization waveguide. The first and second 1x2 bi-directional coupler <NUM> and <NUM> act as polarization-based multiplexers/demultiplexers in that they are bi-directional devices and are used to concurrently split the light from an input fiber according to its polarization states (e.g., into vertical and horizontal) and combine two orthogonally-polarized beams into a single, dual polarization beam. In the example of <FIG> the first and second 1x2 bi-directional coupler <NUM> and <NUM> are polarized along a slow axis of the system <NUM> which lies along the horizontal direction.

The second 1x2 bi-directional coupler <NUM> receives the light signal from the first 1x2 bi-directional coupler <NUM> via the second optical fiber <NUM>. The second 1x2 bi-directional coupler <NUM> outputs the light signal on a second optical waveguide <NUM>. The second 1x2 bi-directional coupler <NUM> also receives the first modulated light signal via the fifth optical waveguide <NUM> and outputs the first modulated light signal on the second optical fiber <NUM> via the first optical waveguide <NUM>. The second 1x2 bi-directional coupler <NUM> receives a light signal via a slow (e.g., horizontal) axis of the second optical fiber <NUM> and outputs a light signal via a fast (e.g., vertical) axis of the second optical fiber <NUM>.

The modulator module <NUM> further includes an optical modulator <NUM> (e.g., a 1x2 directional coupler modulator, a silicon micro resonator optical modulator, or any other optical modulator that produces an output signal that can be redirected to the non-cryogenic environment <NUM>) in the cryogenic environment <NUM>. Thus, this redirected output signal is not dissipated into the cryogenic environment <NUM>. The optical modulator <NUM> is coupled to the second optical waveguide <NUM>, a third optical waveguide <NUM> (e.g., a <NUM> degrees turn waveguide), and a fourth optical waveguide <NUM>. The optical modulator <NUM> receives the light signal from the second 1x2 directional coupler <NUM> via the second optical waveguide <NUM>. The optical modulator <NUM> modulates this received light signal to produce the first modulated light signal and a second modulated light signal. The optical modulator <NUM> outputs the second modulated light signal to a cryogenic device <NUM>, e.g., a cryogenic computing system, within the cryogenic environment <NUM> that is coupled to the optical modulator <NUM> via the fourth optical waveguide <NUM>. In another example, the cryogenic device <NUM> is part of a cryogenic system (not shown) that provides a communication path within the cryogenic environment <NUM> and/or conveys signals from within the cryogenic environment <NUM> to the non-cryogenic environment <NUM>. The fourth optical waveguide <NUM> is coupled to a third optical fiber <NUM> to provide a data path between the optical modulator <NUM> and the cryogenic device <NUM> for the second modulated light signal. The modulator module <NUM> further includes a polarization rotator <NUM> that is coupled to the third optical waveguide <NUM> and the fifth optical waveguide <NUM>. The optical modulator <NUM> also outputs the first modulated light signal to the polarization rotator <NUM> via the third optical waveguide <NUM>. The optical modulator <NUM> provides two "pseudo-complimentary" optical outputs in which substantially no light is wasted into the substrate of the modulator module <NUM> and which can be read out via the fourth optical waveguide <NUM> and the third optical fiber <NUM>.

The polarization rotator <NUM> is an optical device that rotates the polarization axis of a linearly polarized light beam by an angle of choice. In this example, the polarization rotator <NUM> is a <NUM> degrees polarization rotator and can be integrated optically with the third optical waveguide <NUM> and the fifth optical waveguide <NUM>. The polarization rotator <NUM> receives the first modulated light signal from the optical modulator <NUM> via the third optical waveguide <NUM>, rotates a polarization axis of the first modulated light signal by about <NUM> degrees (e.g., within a <NUM>% tolerance), and outputs the polarization axis rotated version of the first modulated light signal to the second 1x2 directional coupler-<NUM>. The polarization rotator <NUM> outputs the rotated version of the first modulated light signal on the fifth optical waveguide <NUM> to a fast axis (e.g., a vertical axis) of the second 1x2 directional coupler <NUM>. Thus, the system <NUM> redirects one of the outputs of the optical modulator <NUM>, the first modulated light signal on the third optical waveguide <NUM>, from the cryogenic environment <NUM> to the non-cryogenic environment <NUM> to prevent the first modulated light signal from increasing a temperature of the cryogenic environment <NUM>. Moreover, the system <NUM> eliminates the need for a second fiber at the output of the second optical device <NUM> and the associated complexity (e.g., mass, connectors, space, etc.), with the example system <NUM> redirecting one of the two outputs from the optical modulator <NUM> of the system <NUM> without affecting performance of the optical modulator <NUM>. Furthermore, the second optical device <NUM>, the optical modulator <NUM>, and their associated waveguides <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are integrated onto a same substrate, resulting in a diminished loss of light as it moves between such components such that nearly all of the first modulated light signal can be redirected into the non-cryogenic environment <NUM>.

<FIG> illustrates yet another example system <NUM> (e.g., ultra-low power electro-optic cryo-logic system) to redirect unused light from a cryogenic environment <NUM> to a non-cryogenic environment <NUM>. The system <NUM> includes a first optical circulator <NUM> (e.g., an on-chip integrated optical circulator) in the non-cryogenic environment <NUM>. The first optical circulator <NUM> is coupled to a first optical fiber <NUM>, a second optical fiber <NUM> (e.g., a polarization maintaining fiber), and a third optical fiber <NUM> (e.g., a fast axis). The first optical circulator <NUM> receives a light signal on a slow axis of the first optical fiber <NUM> and outputs the light signal on a second optical fiber <NUM>. The second optical fiber <NUM> is a polarization-maintaining (PM) fiber and carries polarized continuous wave (CW) light along its slow (e.g., horizontal) axis. The first optical circulator <NUM> further receives a first modulated light signal on the second optical fiber <NUM> and outputs the first modulated light signal into the non-cryogenic environment <NUM> via the third optical fiber <NUM>. Thus, the second optical fiber <NUM> is a bi-directional path utilized to transport the light signal into the cryogenic environment <NUM> from the non-cryogenic environment <NUM>, and the first modulated light signal into the non-cryogenic environment <NUM> from the cryogenic environment <NUM>, with the light signal being transported into the cryogenic environment <NUM> on a slow axis of the second optical fiber <NUM> and the first modulated light signal being transported on a fast axis of the second optical fiber <NUM>.

The system <NUM> further includes a modulator module <NUM> that is comprised of a second optical circulator <NUM> (e.g., an on-chip integrated optical circulator) in the cryogenic environment <NUM>. The first and second optical circulators <NUM> and <NUM> act as polarization-based multiplexers/demultiplexers in that they are bi-directional devices and are used to simultaneoulsy split the light from an input fiber according to its polarization states (i.e., into vertical and horizontal) and combine two orthogonally-polarized beams into a single, dual polarization beam. In the example of <FIG> the first and second optical circulators <NUM> and <NUM> are polarized along a slow axis of the system <NUM> which lies along the horizontal direction.

The second optical circulator <NUM> receives the light signal from the first optical circulator <NUM> via the second optical fiber <NUM>. The second optical circulator <NUM> is coupled to the second optical fiber <NUM> via a first optical waveguide <NUM>, and is further coupled to a second optical waveguide <NUM> (e.g., a slow axis) and a third optical waveguide <NUM> (e.g., a <NUM> degrees turn waveguide). The second optical circulator <NUM> outputs the light signal on a second optical waveguide <NUM>. The second optical circulator <NUM> also receives the first modulated light signal via the third optical waveguide <NUM> and outputs the first modulated light signal on the second optical fiber <NUM> via the first optical waveguide <NUM>. The second optical circulator <NUM> receives a light signal via a slow (e.g., horizontal) axis of the second optical fiber <NUM> and outputs a light signal via a fast (e.g., vertical) axis of the second optical fiber <NUM>.

The modulator module <NUM> further includes an optical modulator <NUM> (e.g., a 1x2 directional coupler modulator, a silicon micro resonator, or any other optical modulator that produces an output signal that can be redirected to the non-cryogenic environment <NUM>) in the cryogenic environment <NUM>. Thus, this redirected output signal is not dissipated into the cryogenic environment <NUM>. The optical modulator <NUM> is coupled to a second optical waveguide <NUM>, a fifth optical fiber <NUM>, and a third optical waveguide <NUM>. In an example, the optical modulator <NUM> is implemented on a same integrated circuit chip as the second optical circulator <NUM>. The optical modulator <NUM> receives the light signal from the second optical circulator <NUM> via the second optical waveguide <NUM>. The optical modulator <NUM> modulates this received light signal to produce the first modulated light signal and a second modulated light signal. The optical modulator <NUM> outputs the second modulated light signal to a cryogenic device <NUM>, e.g., a cryogenic computing system, within the cryogenic environment 321that is coupled to the optical modulator <NUM> via the fifth optical fiber <NUM>. In another example, the cryogenic device <NUM> is part of a cryogenic system (not shown) that provides a communication path within the cryogenic environment <NUM> and/or conveys signals from within the cryogenic environment <NUM> to the non-cryogenic environment <NUM>. The fifth optical waveguide <NUM> is coupled to a fourth optical fiber <NUM> to provide a data path between the optical modulator <NUM> and the cryogenic device <NUM> for the second modulated light signal. The optical modulator <NUM> also outputs the first modulated light signal to the second optical circulator <NUM> via the third optical waveguide <NUM>. The optical modulator <NUM> provides two "pseudo-complimentary" optical outputs in which substantially no light is wasted into the substrate of the modulator module <NUM> and which can be read out via the fifth optical waveguide <NUM> and the fourth optical fiber <NUM>.

Thus, the system <NUM> redirects one of the outputs of the optical modulator <NUM>, the first modulated light signal on the third optical waveguide <NUM>, from the cryogenic environment <NUM> to the non-cryogenic environment <NUM> where the first modulated light signal will not increase a temperature of the cryogenic environment <NUM>. In particular, the second optical circulator <NUM> receives the first modulated light signal and outputs the first modulated light signal on the second optical fiber <NUM> on which the first modulated light signal will pass to the non-cryogenic environment <NUM>. Thereafter, the first optical circulators <NUM> outputs the first modulated light signal into the non-cryogenic environment <NUM> to prevent the first modulated light signal from increasing a temperature of the cryogenic environment <NUM>. Moreover, the system <NUM> eliminates the need for a second fiber at the output of the second optical circulator <NUM> and the associated complexity (e.g., mass, connectors, space, etc.), with the example system <NUM> redirecting one of the two outputs from the optical modulator <NUM> of the system <NUM> without affecting performance of the optical modulator <NUM>. Furthermore, the second optical circulator <NUM>, the optical modulator <NUM>, and their associated waveguides <NUM>, <NUM>, <NUM>, and <NUM> are integrated onto a same substrate, resulting in a diminished loss of light as it moves between such components such that nearly all of the first modulated light signal can be redirected into the non-cryogenic environment <NUM>.

<FIG> illustrates an example schematic of an optical modulator <NUM> (e.g., a 1x2 directional coupler modulator). In an example, the optical modulator <NUM> can be used as the optical modulator <NUM>, the optical modulator <NUM>, and/or the optical modulator <NUM> illustrated in <FIG>, respectively.

The optical modulator <NUM> includes a single input, e.g., a single mode waveguide input <NUM>. In an example, the optical modulator <NUM> is implemented on an electro-optics (EO) material, such as an organic EO material, a plastic EO material, or a polymer EO material, consisting of nonlinear optical chromophores in a polymer lattice. The single mode waveguide <NUM> branches at a waveguide "Y" <NUM> coupled to a directional coupler that includes two substantially identical parallel, single mode coupled waveguides <NUM> and <NUM>. In an example, this waveguide "Y" is a slow axis polarization waveguide. Electrodes <NUM> are disposed parallel to the two substantially identical parallel, single mode coupled waveguides <NUM> and <NUM>. In an example, the two substantially parallel, single mode coupled waveguides <NUM> and <NUM> are coupled waveguides in that a voltage signal is applied to the electrodes <NUM> to control the optical power P1 and P2 of the two substantially parallel, single mode coupled waveguides <NUM> and <NUM>, respectively, of the optical modulator <NUM>.

<FIG> illustrates an example optical power timing diagram <NUM> for the optical modulator <NUM> illustrated in <FIG>. In particular, with zero input voltage (V=<NUM>) being applied to the electrodes <NUM>, light coupled into the single mode waveguide <NUM> splits evenly between the two substantially identical parallel, single mode coupled waveguides <NUM> and <NUM>. In the case illustrated in <FIG>, the output optical power is P1=P2=<NUM>. When a value of one input voltage (V=<NUM>) is applied to the electrodes <NUM>, a phase mismatch between the two substantially identical parallel, single mode coupled waveguides <NUM> and <NUM> is introduced, eliminating symmetry within the optical modulator <NUM> and causing unequal splitting of light at the two single mode coupled waveguides <NUM> and <NUM>. Depending on the design of the optical modulator <NUM>, one output (e.g., single mode coupled waveguide <NUM>) will be high (optical power=<NUM>) and the other output (e.g., single mode coupled waveguide <NUM>) will be low (optical power =<NUM>). In the example of <FIG>, when V=<NUM> is applied to the electrodes <NUM> the optical power P1 at the single mode coupled waveguide <NUM> is P1=<NUM> whereas at the same time the optical power P2 at single mode coupled waveguide <NUM> is P2=<NUM>. In the example illustrated, the optical modulator <NUM> produces a first modulated light signal at optical power P1 that is a complement of the second modulated light signal at optical power P2 produced by the optical modulator <NUM>.

In view of the foregoing structural and functional features described above, a method in accordance with various aspects of the present disclosure will be better appreciated with reference to <FIG>. While, for purposes of simplicity of explanation, the method of <FIG> is shown and described as executing serially, it is to be understood and appreciated that the present disclosure is not limited by the illustrated order, as some aspects may, in accordance with the present disclosure, occur in different orders and/or concurrently with other aspects from that shown and described herein. Moreover, not all illustrated features may be required to implement a method in accordance with an aspect of the present disclosure. Additionally, the method of <FIG> may include additional features as described above for the components described in <FIG>.

<FIG> illustrates an example method <NUM> of redirect unused light from the cryogenic environment <NUM>, <NUM>, or <NUM> to the non-cryogenic environment <NUM>, <NUM>, or <NUM>. This redirected unused light is not dissipated into the cryogenic environment <NUM>, <NUM>, or <NUM>. At <NUM>, the method <NUM> includes outputting, from a first optical device (e.g., the first optical device <NUM> of <FIG>, the first 1x2 directional coupler <NUM> of <FIG>, and first optical circulator <NUM> of <FIG>) in a non-cryogenic environment <NUM>, <NUM>, or <NUM>, a light signal to a second optical device (e.g., the second optical device <NUM> of <FIG>, the second 1x2 directional coupler <NUM> of <FIG>, and second optical circulator <NUM> of <FIG>) in the cryogenic environment <NUM>, <NUM>, or <NUM>. At <NUM>, the method <NUM> further includes outputting, from the second optical device, the light signal to an optical modulator (e.g., optical modulator <NUM> of <FIG>, optical modulator <NUM> of <FIG>, and optical modulator <NUM> of <FIG>) in the cryogenic environment <NUM>, <NUM>, or <NUM>.

At <NUM>, the method <NUM> even further includes modulating, with the optical modulator, the light signal to produce a first modulated light signal and a second modulated light signal. At <NUM>, the method <NUM> further includes outputting, from the optical modulator, the second modulated light signal. At <NUM>, the method <NUM> yet further includes outputting, from the optical modulator, the first modulated light signal to the second optical device.

At <NUM>, the method even further includes outputting, from the second optical device, the first modulated light signal to the first optical device. At <NUM>, the method <NUM> yet further includes outputting, from the first optical device, the first modulated light signal into the non-cryogenic environment <NUM>, <NUM>, or <NUM>.

Claim 1:
A system (<NUM>, <NUM>, <NUM>), comprising:
a first optical device (<NUM>, <NUM>, <NUM>), in a non-cryogenic environment (<NUM>, <NUM>, <NUM>), suitable to receive a light signal, output the light signal, receive a first modulated light signal, and output the first modulated light signal into the non-cryogenic environment;
a second optical device (<NUM>, <NUM>, <NUM>), in a cryogenic environment (<NUM>, <NUM>, <NUM>), suitable to receive the light signal from the first optical device, output the light signal, receive the first modulated light signal, and output the first modulated light signal to the first optical device;
wherein the system further comprises an optical modulator (<NUM>, <NUM>, <NUM>) and a cryogenic computing device (<NUM>, <NUM>, <NUM>) in the cryogenic environment, suitable to receive the light signal from the second optical device, modulate the light signal to produce the first modulated light signal and a second modulated light signal, output the second modulated light signal to the cryogenic computing device to establish a data path between the optical modulator and the cryogenic computing device, output the first modulated light signal to the second optical device, whereby the first modulated light signal is redirected from the cryogenic environment into the non-cryogenic environment and output the first modulated light signal.