Optical Receiver and Method for Power Control of an Optical Receiver

Abstract

An optical receiver includes an optical amplifier that is optically connected to a local oscillator (LO) of the optical receiver and a plurality of optical hybrid mixers and is electrically connected to a controller. The optical amplifier is configured to receive an optical LO signal from the LO, receive a voltage value associated with an optical input signal of the optical receiver, control the power of the optical LO signal based on the voltage value, and, after adjusting the power of the optical LO signal, provide the optical LO signal to the plurality of optical hybrid mixers. The controller is configured to determine the voltage value associated with the optical input signal and cause the voltage value to be provided to the optical amplifier.

Description

[0001] Cross - Reference to Related Applications

[0002] This patent application claims priority to U.S. Provisional Patent Application No. 63 / 144,239, filed on February 1, 2021, titled "AUTOMATIC POWER CONTROL FOR COHERENT PHOTORECEIVERS" and U.S. Non - Provisional Patent Application No. 17 / 199,170, filed on March 11, 2021, titled "AUTOMATIC POWER CONTROL FOR AN OPTICAL RECEIVER". The disclosure of the prior applications is considered to be part of this patent application and is incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to controlling an optical receiver, and more particularly, to controlling an optical receiver using an automatic power control (APC) mode. Background Art

[0004] An optical receiver can be designed to receive light as an input signal and convert one or more wavelength channels included in the input signal into one or more corresponding electrical signals. This function can be provided by, for example, an optical receiver that includes an integrated optical circuit, a set of photodetectors (PDs), and a set of transimpedance amplifiers (TIAs). In an example operation, the input light is received (via an optical fiber) at the integrated optical circuit. The integrated optical circuit splits the input light into a set of wavelength channels. Next, each wavelength channel is coupled to a corresponding PD in the set of PDs, and the PD converts the wavelength channel from an optical signal into a current. Then, the current signal is provided to a corresponding TIA in the set of TIAs, and the TIA converts the current signal into a voltage signal and outputs the voltage signal (e.g., for further signal processing, as the output of the optical receiver, etc.). Summary of the Invention

[0005] In some embodiments, an optical receiver includes an optical amplifier that is connected to a local oscillator (LO) of the optical receiver and a plurality of optical hybrid mixers, wherein the optical amplifier is configured to: receive an optical LO signal from the LO; receive a voltage value associated with an optical input signal of the optical receiver; adjust the power of the optical LO signal based on the voltage value; and after adjusting the power of the optical LO signal, provide the optical LO signal to the plurality of optical hybrid mixers.

[0006] In some embodiments, an optical receiver includes an optical amplifier optically connected to the LO of the optical receiver and a plurality of optical hybrid mixers, wherein the optical amplifier is configured to: receive an optical LO signal from the optical LO, receive a voltage value associated with an optical input signal of the optical receiver, control the power of the optical LO signal based on the voltage value, and provide the optical LO signal to the plurality of optical hybrid mixers after adjusting the power of the optical LO signal; and a controller configured to: determine a voltage value associated with the optical input signal; and cause the voltage value to be provided to the optical amplifier.

[0007] In some embodiments, a method includes receiving, by a controller of an optical receiver, a plurality of optical signal strength values associated with an optical input signal from a plurality of transimpedance amplifiers (TIAs) of the optical receiver; processing, by the controller, the plurality of optical signal strength values to determine a representative optical signal strength value; determining, by the controller, whether the representative optical signal strength value meets an optical signal strength threshold; generating, by the controller, a control signal based on determining whether the representative optical signal strength value meets the optical signal strength threshold, wherein when the representative optical signal strength value meets the optical signal strength threshold, the control signal indicates that an automatic gain control (AGC) mode is to be used to control the optical receiver, or wherein when the representative optical signal strength value does not meet the optical signal strength threshold, the control signal indicates that an automatic power control (APC) mode is to be used to control the optical receiver; and causing, by the controller, an adjustment of the power of an optical LO signal associated with the optical receiver based on the control signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a schematic diagram of an example optical device described herein.

[0009] Figure 2 is a schematic diagram of an example optical device described herein.

[0010] Figure 3 is a diagram showing a part of a loop controller described herein.

[0011] Figure 4 is a graph showing the bit error rate (BER) performance of an example optical device.

[0012] Figure 5 is Figure 2 a diagram of an example component in one or more components of

[0013] Figure 6 is a flowchart of an example process related to automatic power control (APC) of an optical receiver. Detailed implementation manners

[0014] The following detailed description of the exemplary implementation refers to the accompanying drawings. The same reference numerals in different drawings may identify the same or similar elements.

[0015] Traditional optical receivers (e.g., coherent quadrature amplitude modulation (QAM) optical receivers) use an automatic gain control (AGC) mode to maintain a constant amplitude of the output signal of the traditional optical receiver. Using this AGC mode, the traditional optical receiver fixes the optical power of the optical LO signal generated by the local oscillator (LO) of the traditional optical receiver and automatically adjusts the transimpedance associated with the transimpedance amplifier of the traditional optical receiver. However, the shot noise associated with the optical LO signal is proportional to the optical power of the optical LO signal, and the TIA noise associated with the TIA (e.g., the input noise generated by the TIA) is inversely proportional to the transimpedance (and thus proportional to the optical power of the optical LO signal in the traditional optical receiver). Therefore, a high LO power generates high shot noise and high TIA noise. Traditional optical receivers typically operate at a constant, maximum optical power of the optical LO signal, thereby generating shot noise and TIA noise, which affect the sensitivity of the traditional optical receiver (e.g., by affecting the amount of transimpedance that can be controlled using the AGC mode). This also degrades the bit error rate (BER) performance of the traditional coherent optical receiver.

[0016] Some implementations described herein provide an optical receiver (e.g., a coherent optical receiver) that uses an automatic power control (APC) mode to control the optical receiver (e.g., to maintain a constant amplitude of the electrical output signal of the optical receiver). The optical receiver using the APC mode fixes a set of TIAs of the optical receiver to have a constant transimpedance and uses an optical amplifier of the optical receiver to adjust the power (e.g., optical power) of the optical LO signal generated by the LO of the optical receiver. Thus, when using the APC mode, the optical receiver causes the power of the optical LO signal to vary and thus be less than the maximum power of the optical LO signal during one or more operating periods of the optical receiver (as opposed to when using the AGC mode, which causes the power of the optical LO signal to be fixed at the maximum power of the optical LO signal). Thus, compared to the amount of shot noise and TIA noise associated with controlling a conventional optical receiver using the AGC mode, when using the APC mode, the optical receiver reduces the amount of shot noise and TIA noise associated with controlling the optical receiver. Thus, compared to a conventional optical receiver, the optical receiver has increased sensitivity and provides improved BER performance. In addition, due to the reduced power of the optical LO signal, the durability of the optical receiver (e.g., with respect to environmental conditions and aging of the optical receiver components) is improved compared to a conventional optical receiver.

[0017] In addition, the APC mode requires a constant, fixed transimpedance for the set of TIAs, which reduces the design complexity of each TIA of the optical receiver (compared to the design of TIAs with adjustable transimpedance in a conventional optical receiver). In addition, this reduces the size of the TIA, thereby reducing the complexity and cost associated with designing, manufacturing, and maintaining the TIA. In addition, the reduced input dynamic range and constant, fixed transimpedance of the TIA reduce the power consumption of the TIA. Thus, the set of TIAs of the optical device can support high bandwidth (e.g., 96 / 128 Gbaud) and high TIA linearity (e.g., 128QAM).

[0018] Some embodiments described herein provide a loop controller for an optical receiver. The loop controller can be configured to receive an optical signal strength value indicating the power (e.g., optical power) of the optical input signal of the optical receiver from a set of TIAs of the optical receiver. Based on the optical signal strength value, the loop controller can cause the optical receiver to be controlled using the AGC mode or the APC mode. Thus, the loop controller can allow the optical receiver to provide preferred performance (e.g., in terms of examples such as shot noise, TIA noise, sensitivity, or bit error rate performance) based on the power of the optical input signal.

[0019] Figure 1is a schematic diagram of an example optical device 100 (e.g., an optical receiver) described herein. As further described herein, an automatic power control (APC) mode can be used to control the optical device 100. As Figure 1 shown, the optical device 100 can include a signal input 102, a local oscillator (LO) 104, an optical amplifier 106, a beam splitter (BS) 108, a polarization beam splitter (PBS) 110, a plurality of optical hybrid mixers 112 (shown as optical hybrid mixer 112-1 and optical hybrid mixer 112-2), a plurality of photodetectors (PDs) 114 (shown as eight PDs 114), a plurality of transimpedance amplifiers (TIAs) 116 (shown as TIA116-1 to 116-4), and / or a combiner 118.

[0020] As Figure 1 further shown, the signal input 102 can be connected (e.g., optically connected) to the BS108. The signal input 102 can be configured to receive an optical input signal from an input source (e.g., an optical fiber (not shown)) and provide the optical input signal (e.g., without amplification) to the BS108. In some embodiments, the BS108 can be connected (e.g., optically connected) to the plurality of optical hybrid mixers 112. For example, as Figure 1 shown, the BS108 can be connected to the optical hybrid mixer 112-1 and the optical hybrid mixer 112-2. The BS108 can be configured to split the optical input signal (e.g., the optical input signal received by the BS108 from the signal input 102) into a plurality of optical input signal portions and provide the plurality of optical input signal portions to the plurality of optical hybrid mixers 112, respectively. For example, the BS108 can split the optical input signal into a first optical input signal portion and a second optical input signal portion and can send the first optical input signal portion to the optical hybrid mixer 112-1 and the second optical input signal portion to the optical hybrid mixer 112-2.

[0021] In some embodiments, the LO 104 (e.g., an LO laser device) can be configured to generate an optical LO signal. For example, the LO 104 can generate an optical LO signal having a constant, fixed power (e.g., optical power). As Figure 1Further shown, LO 104 may be connected (e.g., optically connected) to an optical amplifier 106. The optical amplifier 106 may be an example of a solid-state optical amplifier, a doped fiber optical amplifier, or a semiconductor optical amplifier (SOA). In some embodiments, LO 104 and the optical amplifier 106 may be included in an integrated tunable laser assembly (ITLA). LO 104 may be configured to provide an optical LO signal to the optical amplifier 106. The optical amplifier 106 may be configured to adjust the power of the optical LO signal and provide the optical LO signal to PBS 110 (e.g., after adjusting the power of the optical LO signal). Further details regarding the adjustment of the power of the optical LO signal by the optical amplifier 106 are described below.

[0022] In some embodiments, PBS 110 may be connected (e.g., optically connected) to a plurality of optical hybrid mixers 112. For example, as Figure 1 shown, PBS 110 may be connected to an optical hybrid mixer 112-1 and an optical hybrid mixer 112-2. PBS 110 may be configured to divide the optical LO signal (e.g., the optical LO signal received by PBS 110 from the optical amplifier 106) into a plurality of optically polarized optical LO signal portions and provide the plurality of optical LO signal portions to the plurality of optical hybrid mixers 112. For example, PBS 110 may divide the optical LO signal into a first optical LO signal portion and a second optical LO signal portion and may send the first optical LO signal portion to the optical hybrid mixer 112-1 and the second optical LO signal portion to the optical hybrid mixer 112-2.

[0023] In some embodiments, an optical hybrid mixer 112 among the plurality of optical hybrid mixers 112 may be connected (e.g., optically connected) to a set of PDs 114 among the plurality of PDs 114. For example, as Figure 1 shown, the optical hybrid mixer 112-1 may be connected to a first set of PDs 114-1 (e.g., Figure 1 the top four PDs 114 shown), and the optical hybrid mixer 112-2 may be connected to a second set of PDs 114-2 (e.g., Figure 1The four bottom PDs shown (114). An optical hybrid mixer 112 among the multiple optical hybrid mixers 112 can be configured to mix an optical input signal portion (e.g., received by the optical hybrid mixer 112 from BS108) and an optical LO signal portion (e.g., received by the optical hybrid mixer 112 from PBS 110) into a mixed optical output signal, and provide the mixed optical output signal to a set of PDs 114 connected to the optical hybrid mixer 112. For example, the optical hybrid mixer 112-1 can mix a first optical input signal portion provided by BS108 and a first optical LO signal portion provided by PBS110 into a first mixed optical output signal, and can provide the first mixed optical output signal to the first set of PDs 114-1. As another example, the optical hybrid mixer 112-2 can mix a second optical input signal portion provided by BS108 and a second optical LO signal portion provided by PBS110 into a second mixed optical output signal, and can provide the second mixed optical output signal to the second set of PDs 114-2.

[0024] In some embodiments, a set of PDs 114 can include multiple subsets of PDs 114, where a subset of PDs 114 (e.g., a subset composed of two PDs 114) is connected (e.g., optically connected) to the optical hybrid mixer 112. For example, as Figure 1 shown, a set of PDs 114-1 can include a subset of PDs 114-1-a and a subset of PDs 114-1-b connected to the optical hybrid mixer 112-1, and a set of PDs 114-2 can include a subset of PDs 114-2-a and a subset of PDs 114-2-b connected to the optical hybrid mixer 112-2. Thus, the PDs 114 in the subset of PDs 114 can be configured to receive a portion of the mixed optical output signal provided by the optical hybrid mixer 112 to the subset of PDs 114. For example, the first PD 114 in the subset of PDs 114-1-a can receive a portion of the first mixed optical output signal provided by the optical hybrid mixer 112-1 to the set of PDs 114-1. As another example, the second PD 114 in the subset of PDs 114-2-b can receive a portion of the second mixed optical output signal provided by the optical hybrid mixer 112-2 to the set of PDs 114-2.

[0025] The subset of PDs 114 can be connected (e.g., electrically connected) to a TIA 116 among the multiple TIAs 116. For example, as Figure 1As shown, PD subset 114-1-a can be connected to TIA 116-1, PD subset 114-1-b can be connected to TIA 116-2, PD subset 114-2-a can be connected to TIA 116-3, and PD subset 114-2-b can be connected to TIA 116-4. Thus, the PD 114 in PD 114 subset can be configured to convert a portion of the mixed optical output signal (e.g., provided to PD114 by optical hybrid mixer 112) into an electrical output signal and provide the electrical output signal to the TIA 116 among the plurality of TIAs 116 connected to this PD 114. For example, the first PD 114 in PD subset 114-1-a can convert a portion of the first mixed optical output signal into a first electrical output signal and can provide the first electrical output signal to TIA 116-1. As another example, the second PD 114 in PD subset 114-1-b can convert a portion of the second mixed optical output signal into a second electrical output signal and can provide the second electrical output signal to TIA 116-3.

[0026] The plurality of TIAs 116 can be connected (e.g., electrically connected) to a processing component ( Figure 1 not shown in the figure), such as a digital signal processor (DSP). The TIA 116 among the plurality of TIAs 116 can be configured to amplify the electrical output signal (e.g., received by TIA 116 from PD114) and can provide the electrical output signal to the processing component for processing. For example, TIA 116-1 can receive the first electrical output signal from the first PD 114 in PD subset 114-1-a, can amplify the first electrical output signal, and can provide the first electrical output signal to the DSP for processing. As another example, TIA 116-3 can receive the second electrical output signal from the second PD 114 in PD subset 114-2-2, can amplify the second electrical output signal, and can provide the second electrical output signal to the DSP for processing.

[0027] In some embodiments, the plurality of TIAs 116 can be respectively connected (e.g., electrically connected) to combiner 118. For example, as Figure 1As shown, each of TIA 1161, TIA 116-2, TIA 116-3, and TIA 116-4 is connected to combiner 118. The TIA 116s among the multiple TIAs 116 can be configured to provide voltage values associated with an electrical output signal (e.g., received by TIA 116 from PD 114) to combiner 118. For example, TIA 116-1 can determine the peak detection voltage (also referred to as PKD) of a first electrical output signal (e.g., received by TIA 116-1 from the first PD 114 in PD subset 114-1-a), and can send a first voltage value indicating the peak detection voltage of the first electrical output signal to combiner 118. As another example, TIA 116-3 can determine the peak detection voltage of a second electrical output signal (e.g., received by TIA 116-3 from the second PD 114 in PD subset 114-2-b), and can send a second voltage value indicating the peak detection voltage of the second electrical output signal to combiner 118.

[0028] Combiner 118 can be configured to receive multiple voltage values from the multiple TIAs 116. For example, combiner 118 can receive a first voltage value from TIA 116-1, a second voltage value from TIA 116-3, a third voltage value from TIA 116-2, and so on. Combiner 118 can be configured to process the multiple voltage values to determine a representative voltage value. For example, combiner 118 can determine that the representative voltage value is the average (e.g., mean or weighted mean), median, maximum, or minimum of the multiple voltage values.

[0029] As Figure 1As shown, combiner 118 can be connected (e.g., electrically connected) to optical amplifier 106. In some embodiments, combiner 118 can be configured to provide a representative voltage value to optical amplifier 106. Optical amplifier 106 can be configured to adjust the power of the optical LO signal based on the representative voltage value (e.g., the voltage value received by optical amplifier 106 from combiner 118). For example, when the representative voltage value meets (e.g., is greater than or equal to) a first voltage value threshold, optical amplifier 106 can adjust the power of the optical LO signal such that the power of the optical LO signal does not meet (e.g., is less than) a first power threshold. As an additional or alternative example, when the representative voltage value does not meet (e.g., is less than) a second voltage value threshold, optical amplifier 106 can adjust the power of the optical LO signal such that the power of the optical LO signal meets (e.g., is greater than or equal to) a second power threshold. In this way, optical amplifier 106 can be configured to: reduce the power of the optical LO signal when the representative voltage value is high; and / or increase the power of the optical LO when the representative voltage value is low. Thus, optical amplifier 106 can be configured to make the optical LO signal have a specific power or a specific power range based on the representative voltage value. Additionally or alternatively, although the examples provided illustrate discrete control of the power of the optical LO signal, expected implementations include continuous control of the power of the optical LO signal. For example, optical amplifier 106 can be configured to make the optical LO signal have a continuously varying power or power range based on a continuously varying representative voltage value. In this way, the APC mode can be used to control optical device 100.

[0030] After adjusting the power of the optical LO signal to facilitate control of optical device 400 using the APC mode, optical amplifier 106 can provide the optical LO signal to PBS 110 (e.g., after adjusting the power of the optical LO signal). The optical LO signal can then be processed as described above.

[0031] As described above, Figure 1 is provided only as an example. Other examples are possible and may be different from those Figure 1 described.

[0032] Figure 2 is a schematic diagram of an example optical device 200 (e.g., an optical receiver) described herein. As further described herein, an automatic power control (APC) mode and / or an automatic gain control (AGC) mode can be used to control optical device 200. As Figure 2As shown, the optical device 200 may include a signal input 102, a local oscillator (LO) 104, an optical amplifier 106, a beam splitter (BS) 108, a polarization beam splitter (PBS) 110, a plurality of optical hybrid mixers 112 (shown as optical hybrid mixer 112-1 and optical hybrid mixer 112-2) and / or a plurality of photodetectors (PD) 114 (shown as eight PDs 114), as described herein with respect to Figure 1 as described. As Figure 2 further shown in, the optical device may include a plurality of transimpedance amplifiers (TIAs) 202 (shown as TIA 202-1 to 202-4), a loop controller 204 and / or an optical amplifier controller 206.

[0033] As described above with respect to Figure 1 as described, the signal input 102 may receive an optical input signal from an input source and may provide the optical input signal (e.g., without amplification) to the BS 108, which may divide the optical input signal into a plurality of optical input signal portions and may provide the plurality of optical input signal portions to the plurality of optical hybrid mixers 112. The LO 104 may generate an optical LO signal and may provide the optical LO signal to the optical amplifier 106. In some embodiments, the optical amplifier 106 may adjust the power of the optical LO signal (as further described below) and may provide the optical LO signal (e.g., after adjusting the power of the optical LO signal) to the PBS 110, which may divide the optical LO signal into a plurality of optically polarized LO signal portions and may provide the plurality of optical LO signal portions to the plurality of optical hybrid mixers 112.

[0034] As described above with respect to Figure 1 further described, each of the plurality of optical hybrid mixers 112 may mix an optical input signal portion (e.g., received by the optical hybrid mixer 112 from the BS 108) and an optical LO signal portion (e.g., received by the optical hybrid mixer 112 from the PBS 110) into a mixed optical output signal and may provide the mixed optical output signal to a set of PDs 114 connected to the optical hybrid mixer 112. The PDs 114 in a subset of the set of PDs 114 may receive a portion of the mixed optical output signal.

[0035] As Figure 2 shown, the PD 114 subset may be connected (e.g., electrically connected) to the TIA 202 in the plurality of TIAs 202. For example, as Figure 2As shown, PD subset 114-1-a can be connected to TIA 202-1, PD subset 114-1-b can be connected to TIA 202-2, PD subset 114-2-a can be connected to TIA 202-3, and PD subset 114-2-b can be connected to TIA 202-4. Thus, the PD 114 in the PD 114 subset can be configured to convert a portion of the mixed optical output signal (e.g., provided to the PD 114 by the optical hybrid mixer 112) into an electrical output signal and provide the electrical output signal to the TIA 202 among the plurality of TIAs 202 to which the PD 114 is connected. For example, the first PD 114 of PD subset 114-1-a can convert a portion of the first mixed optical output signal into a first electrical output signal and can provide the first electrical output signal to TIA 202-1. As another example, the second PD 114 of PD subset 114-1-b can convert a portion of the second mixed optical output signal into a second electrical output signal and can provide the second electrical output signal to TIA 202-3.

[0036] The plurality of TIAs 202 can be connected (e.g., electrically connected) to a processing component ( Figure 2 not shown in the figure), such as a DSP. The TIA 202 among the plurality of TIAs 202 can be configured to amplify the electrical output signal (e.g., the signal received by the TIA 202 from the PD 114) and can provide the electrical output signal to the processing component for processing. For example, TIA 202-1 can receive the first electrical output signal from the first PD 114 in PD subset 114-1-a, can amplify the first electrical output signal, and can provide the first electrical output signal to the DSP for processing. As another example, TIA 202-3 can receive the second electrical output signal from the second PD 114 in PD subset 114-2-b, can amplify the second electrical output signal, and can provide the second electrical output signal to the DSP for processing.

[0037] In some embodiments, the plurality of TIAs 202 can be respectively connected (e.g., electrically connected) to the loop controller 204. For example, as Figure 2As shown, TIA2021, TIA202-2, TIA202-3, and TIA202-4 are all connected to loop controller 204. In some embodiments, the TIA 202 among the multiple TIAs 202 may be configured to provide the loop controller 204 with an optical signal intensity value associated with the electrical output signal (e.g., received by the TIA 202 from the PD 114) and / or one or more voltage values associated with the electrical output signal. For example, TIA 202-1 may determine the received signal strength (also referred to as RSS), peak detection voltage (also referred to as PKD), and / or gain control voltage (also referred to as VGC) of the first electrical output signal (e.g., received by the TIA 202-1 from the first PD 114 in the PD subset 114-1-a). TIA 202-1 may send to the loop controller 204 a first optical signal intensity value indicating the RSS of the first electrical output signal, a first peak voltage value indicating the PKD of the first electrical output signal, and / or a first gain control voltage value indicating the VGC of the first electrical output signal. As another example, TIA 202-3 may determine the RSS, PKD, and / or VGC of the second electrical output signal (e.g., received by the TIA 202-3 from the second PD 114 in the PD subset 114-2-b). TIA 202-1 may send to the loop controller 204 a second optical signal intensity value indicating the RSS of the second electrical output signal, a second peak voltage value indicating the PKD of the second electrical output signal, and / or a second gain control voltage value indicating the VGC of the second electrical output signal.

[0038] The loop controller 204 may be configured to receive multiple optical signal intensity values from the multiple TIAs 202. For example, the loop controller may receive a first optical signal intensity value from TIA 202-1, a second optical signal intensity value from TIA 202-3, a third optical signal intensity value from TIA 202-2, and so on. The loop controller 204 may be configured to process the multiple optical signal intensity values to determine a representative optical signal intensity value. For example, the loop controller 204 may determine that the representative optical signal intensity value is the average (e.g., mean or weighted mean), median, maximum, or minimum of the multiple optical signal intensity values.

[0039] Additionally or alternatively, the loop controller 204 can be configured to receive a plurality of peak voltage values from a plurality of TIAs 202. For example, the loop controller can receive a first peak voltage value from TIA 202-1, a second peak voltage value from TIA 202-3, a third peak voltage value from TIA 202-2, and so on. The loop controller 204 can be configured to process the plurality of peak voltage values (e.g., when controlling the optical device 200 using the APC mode) to determine a representative peak voltage value. For example, the loop controller 204 can determine that the representative peak voltage value is the average (e.g., mean or weighted mean), median, maximum, or minimum of the plurality of peak voltage values.

[0040] Additionally or alternatively, the loop controller 204 can be configured to receive a plurality of gain control voltage values from a plurality of TIAs 202. For example, the loop controller can receive a first gain control voltage value from TIA 202-1, a second gain control voltage value from TIA 202-3, a third gain control voltage value from TIA 202-2, and so on. The loop controller 204 can be configured to process the plurality of gain control voltage values (e.g., when controlling the optical device 200 using the AGC mode) to determine a representative gain control voltage value. For example, the loop controller 204 can determine that the representative gain control voltage value is the average (e.g., mean or weighted mean), median, maximum, or minimum of the plurality of gain control voltage values.

[0041] As Figure 2 shown, the loop controller 204 can be connected (e.g., electrically connected) to the optical amplifier controller 206. In some embodiments, the loop controller 204 can be configured to determine whether a representative optical signal intensity value meets (e.g., is greater than or equal to) an optical signal intensity threshold to determine whether to use the AGC mode or the APC mode to control the optical device 200. For example, when the loop controller 204 determines that the optical signal intensity value meets (e.g., is greater than or equal to) the optical signal intensity threshold, the loop controller 204 can determine to use the AGC mode to control the optical device 200. Thus, the loop controller 204 can generate a control signal that instructs the optical amplifier controller 206 not to control the optical amplifier 106. Additionally or alternatively, the loop controller 204 can use the AGC mode (e.g., in a manner similar to that described above) to control the plurality of TIAs 202 based on the plurality of gain control voltage values (e.g., received by the loop controller 204 from the plurality of TIAs 202) and / or the representative gain control voltage value (e.g., determined by the loop controller 204).

[0042] As another example, when the loop controller 204 determines that the optical signal strength value does not meet (e.g., is less than) the optical signal strength threshold, the loop controller 204 may determine to use the APC mode to control the optical device 200. Accordingly, the loop controller 204 may generate a control signal that instructs the optical amplifier controller 206 to control the optical amplifier 106.

[0043] The loop controller 204 may be configured to provide the control signal to the optical amplifier controller 206 (e.g., which instructs the optical amplifier controller 206 to control the optical amplifier 106 or not to control the optical amplifier 106). Additionally or alternatively, the loop controller 204 may be configured to provide a representative peak voltage value to the optical amplifier controller 206 (e.g., determined by the loop controller 204 based on multiple peak voltage values received from multiple TIAs 202).

[0044] As Figure 2 shown, the optical amplifier controller 206 may be connected (e.g., electrically connected) to the optical amplifier 106. In some embodiments, the optical amplifier controller 206 may be configured to process the control signal to determine whether the optical amplifier controller 206 is to control the optical amplifier 106 (e.g., using the APC mode). For example, the optical amplifier controller 206 may parse the control signal to determine that the optical amplifier controller 206 is to control the optical amplifier 106. Accordingly, the optical amplifier controller 206 may be configured to provide a representative peak voltage value (e.g., received by the optical amplifier controller 206 from the loop controller 204) to the optical amplifier 106 (e.g., to facilitate controlling the optical device 200 using the APC mode). Alternatively, the optical amplifier controller 206 may parse the control signal to determine that the optical amplifier controller 206 is not to control the optical amplifier 106. Accordingly, the optical amplifier controller 206 may be configured to provide a default voltage value (e.g., indicating to use the AGC mode to control the optical device, as further described below) to the optical amplifier 106 (e.g., to facilitate controlling the optical device 200 using the AGC mode).

[0045] The optical amplifier 106 can be configured to receive a voltage value (e.g., a representative peak voltage value or a default voltage value) from the optical amplifier controller 206. The optical amplifier 106 can adjust the power of the optical LO signal based on the received voltage value. For example, when the received voltage value meets (e.g., is greater than or equal to) a first voltage value threshold, the optical amplifier 106 can adjust the power of the optical LO signal such that the power of the optical LO signal does not meet (e.g., is less than) a first power threshold. As an additional or alternative example, when the received voltage value does not meet (e.g., is less than) a second voltage value threshold, the optical amplifier 106 can adjust the power of the optical LO signal such that the power of the optical LO signal meets (e.g., is greater than or equal to) a second power threshold. In this way, the optical amplifier 106 can be configured to: reduce the power of the optical LO signal when the received voltage value is high; and / or increase the power of the optical LO when the received voltage value is low. Thus, the optical amplifier 106 can be configured to make the optical LO signal have a specific power or a specific power range based on the received voltage value. Additionally or alternatively, although the examples provided illustrate discrete control of the power of the optical LO signal, expected implementations include continuous control of the power of the optical LO signal. For example, the optical amplifier 106 can be configured to make the optical LO signal have a continuously varying power or power range based on a continuously varying representative voltage value.

[0046] In some embodiments, when the received voltage value is the default voltage value (e.g., which indicates that the AGC mode is to be used to control the optical device), the optical amplifier 106 can make the optical LO signal have a specific power (e.g., a high fixed constant power) to facilitate the loop controller 204 to control the plurality of TIAs 202 according to the AGC mode. In some embodiments, when the received voltage value is the representative peak voltage value (e.g., which indicates that the APC mode is to be used to control the optical device), the optical amplifier 106 can make the optical LO signal have a dynamically varying power to facilitate the optical amplifier controller 206 to control the optical amplifier 106 according to the APC mode.

[0047] After adjusting and / or maintaining the power of the optical LO signal to facilitate controlling the optical device 200 using the APC mode or the AGC mode, the optical amplifier 106 can provide the optical LO signal to the PBS 110. Then the optical LO signal can be processed as described above.

[0048] As described above, Figure 2 is provided only as an example. Other examples are possible and may be different from those Figure 2 described.

[0049] Figure 3FIG. 300 shows a portion of the loop controller 204 (e.g., a portion of the loop controller 204 associated with a particular TIA 202 among the plurality of TIAs 202). As Figure 3 shown, the loop controller 204 may be connected (e.g., electrically connected) to a TIA 202 (not shown) among the plurality of TIAs 202 via a first connection 302 and a second connection 304. The first connection 302 may be configured to transmit the voltage value of the electrical output signal, such as the peak detection voltage value (e.g., which indicates the peak detection voltage of the electrical output signal, also referred to as PKD), from the TIA 202 to the loop controller 204. The second connection 304 may be configured to transmit a different voltage value of the electrical output signal, such as the gain control voltage value (e.g., which indicates the gain control voltage of the electrical output signal, also referred to as VGC), from the TIA 202 to the loop controller 204. The loop controller 204 may process the peak detection voltage value and the gain control voltage value, as described above with respect to Figure 2 the description.

[0050] In some embodiments, the loop controller 204 may facilitate the calibration of the optical device 200 to allow the optical device 200 to provide optimal performance when controlled using the APC mode. For example, the loop controller 204 may generate different control signals and / or representative peak voltage values (e.g., adjusting the power of the optical LO signal to a specific level or across different ranges). As indicated by reference numeral 306, the loop controller 204 may then receive and process the respective gain control voltage values of the plurality of TIAs 202 to determine the respective optimal transimpedance gains of the plurality of TIAs 202, which allows each TIA 202 to provide an optimal amplified electrical output signal when controlled using the APC mode. Thus, when the loop controller 204 determines to use the AGC mode to control the optical device, the loop controller 204 may cause the plurality of TIAs 202 to operate at their respective optical transimpedance gains (e.g., as described with respect to Figure 2 the description).

[0051] As indicated by reference numeral 308, the loop controller 204 may control the optical device 200 using the APC mode based on the plurality of peak voltage values provided by the plurality of TIAs 202 (e.g., as described with respect to Figure 2 the description). As indicated by reference numeral 310, the loop controller 204 may control the optical device 200 using the AGC mode based on the plurality of peak voltage values and the plurality of gain control voltage values provided by the plurality of TIAs 202 (e.g., as described with respect to Figure 2 the description).

[0052] As described above, Figure 3 is provided only as an example. Other examples are possible and may be related to the description with respect to Figure 3Described differently.

[0053] Figure 4 Chart 400 shows the bit error rate (BER) performance of an exemplary optical device (e.g., optical device 100 or optical device 200), which is, for example, a 32Gbaud DP-16QAM optical device. The optical device may include a plurality of transimpedance amplifiers (TIAs) (e.g., TIA116 or TIA202), and the maximum transimpedance of each transimpedance amplifier (shown as Z Figure 4 in TDmax ) is 5809 ohms, and the input-referred noise density (shown as IRND in Figure 4 ) is 18 pA / √Hz. In addition, the optical input signal may have an optical power of -22 dBm.

[0054] The optical device may be associated with a signal-to-noise ratio (SNR), and the SNR can be determined using the following formula:

[0055] where: q is the electron charge, ρ is the effective responsivity (A / W), P LO is the CW power (W) of the LO laser, P SIG is the average input signal optical power (W), i n,TIA is the input-referred noise power density of the TIA and B n is the noise bandwidth (Hz). 4qρP LO can be referred to as LO shot noise.

[0056] In a typical case, ρ = 0.06 A / W and P LO = 20 mW (13 dBm). Therefore, the LO shot noise generates a noise current density at the TIA input, which is according to the following formula: Therefore, when (e.g., when the LO shot noise is much larger than the TIA noise), the SNR is not based on the LO power, and thus reaches a constant value according to the following formula In addition, alternatively, when (e.g., when the TIA noise is much larger than the LO shot noise), the SNR increases based on the LO power according to the formula Therefore, in the AGC mode, the TIA noise is not constant and may increase monotonically with respect to the LO power.

[0057] As Figure 4 shown, when using the APC mode, the optical signal-to-noise ratio (OSNR) of the optical device is approximately 22.92 decibels in order to generate 1.40e -02BER (e.g., the optimal BER of the optical device). As Figure 4 Further shown, when using the AGC mode, the OSNR of the optical device is approximately 24.67 dB in order to produce a BER of 1.40e -02 BER. Thus, compared with the AGC mode, the AGC mode provides an OSNR performance improvement of approximately 1.75 dB. Additionally, the lower limit of the BER of the APC mode (e.g., approximately 6.27e -04 ) is lower than the lower limit of the BER of the AGC mode (e.g., 2.923e- 03 ). Thus, for this configuration of the optical device and the optical power of the optical input signal, compared with the AGC mode, the AGC mode provides improved performance.

[0058] As described above, Figure 4 is provided only as an example. Other examples are possible and may be different from those described with respect to Figure 4 described.

[0059] Figure 5 is a diagram of an example component of device 500, which may correspond to loop controller 204 and / or optical amplifier controller 206. In some embodiments, loop controller 204 and / or optical amplifier controller 206 may include one or more devices 500 and / or one or more components of device 500. As Figure 5 shown, device 500 may include bus 510, processor 520, memory 530, storage component 540, input component 550, output component 560, and communication component 570.

[0060] Bus 510 includes components that enable wired and / or wireless communication between the components of device 500. Processor 520 includes a central processing unit, a graphics processing unit, a microprocessor, a controller, a microcontroller, a digital signal processor, a field programmable gate array, an application specific integrated circuit, and / or other types of processing components. Processor 520 is implemented in hardware, firmware, or a combination of hardware and software. In some embodiments, processor 520 includes one or more processors that can be programmed to perform functions. Memory 530 includes random access memory, read only memory, and / or another type of memory (e.g., flash memory, magnetic memory, and / or optical memory).

[0061] The storage component 540 stores information and / or software related to the operation of the device 500. For example, the storage component 540 may include a hard disk drive, a disk drive, an optical disk drive, a solid state disk drive, an optical disk, a digital versatile disk, and / or another type of non-transitory computer-readable medium. The input component 550 enables the device 500 to receive input, such as user input and / or sensed input. For example, the input component 550 may include a touch screen, a keyboard, a keypad, a mouse, buttons, a microphone, switches, sensors, a global positioning system component, an accelerometer, a gyroscope, and / or an actuator. The output component 560 enables the device 500 to provide output, for example, via a display, a speaker, and / or one or more light-emitting diodes. The communication component 570 enables the device 500 to communicate with other devices, for example, via a wired connection and / or a wireless connection. For example, the communication component 570 may include a receiver, a transmitter, a transceiver, a modem, a network interface card, and / or an antenna.

[0062] The device 500 may perform one or more of the processes described herein. For example, a non-transitory computer-readable medium (e.g., the memory 530 and / or the storage component 540) may store a set of instructions (e.g., one or more instructions, code, software code, and / or program code) for execution by the processor 520. The processor 520 may execute the set of instructions to perform one or more of the processes described herein. In some embodiments, execution of the instruction set by one or more processors 520 causes the one or more processors 520 and / or the device 500 to perform one or more of the processes described herein. In some embodiments, hardwired circuitry may be used in place of or in combination with the instructions to perform one or more of the processes described herein. Accordingly, the implementations described herein are not limited to any particular combination of hardware circuitry and software.

[0063] Figure 5 The number and arrangement of the components shown are provided as an example. The device 500 may include additional components, fewer components, different components, or differently arranged components compared to the Figure 5 components shown. Additionally or alternatively, a set of components (e.g., one or more components) of the device 500 may perform one or more functions described as being performed by another set of components of the device 500.

[0064] Figure 6 is a flowchart of an example process 600 associated with automatic power control (APC) of an optical receiver. In some implementations, Figure 6 one or more of the process blocks may be performed by a controller (e.g., the loop controller 204). In some implementations, Figure 6One or more of the process blocks may be performed by another device or set of devices separate from or including the controller, such as an optical amplifier controller (e.g., optical amplifier controller 206). Additionally or alternatively, Figure 6 one or more of the processing blocks may be performed by one or more components of device 500, such as processor 520, memory 530, storage component 540, input component 550, output component 560, and / or communication component 570.

[0065] As Figure 6 shown, process 600 may include receiving a plurality of optical signal intensity values associated with an optical input signal from a plurality of transimpedance amplifiers (TIAs) of an optical receiver (block 610). For example, as described above, the controller may receive a plurality of optical signal intensity values associated with the optical input signal from a plurality of TIAs of the optical receiver.

[0066] As Figure 6 further shown, process 600 may include processing the plurality of optical signal intensity values to determine a representative optical signal intensity value (block 620). For example, as described above, the controller may process the plurality of optical signal intensity values to determine a representative optical signal intensity value.

[0067] As Figure 6 further shown, process 600 may include determining whether the representative optical signal intensity value meets an optical signal intensity threshold (block 630). For example, as described above, the controller may determine whether the representative optical signal intensity value meets the optical signal intensity threshold.

[0068] As Figure 6 further shown, process 600 may include generating a control signal based on determining whether the representative optical signal intensity value meets the optical signal intensity threshold (block 640). For example, as described above, the controller may generate a control signal based on determining whether the representative optical signal intensity value meets the optical signal intensity threshold. In some embodiments, when the representative optical signal intensity value meets the optical signal intensity threshold, the control signal indicates that an automatic gain control (AGC) mode is to be used to control the optical receiver. In some embodiments, when the representative optical signal intensity value does not meet the optical signal intensity threshold, the control signal indicates that an APC mode is to be used to control the optical receiver.

[0069] As Figure 6As further shown in, process 600 may include causing an adjustment of the power of an optical local oscillator (LO) signal associated with an optical receiver based on a control signal (block 650). For example, as described above, the controller may cause an adjustment of the power of the optical LO signal associated with the optical receiver based on the control signal. In some embodiments, causing the adjustment of the optical LO signal power includes providing the control signal to another component of the optical receiver such that an optical amplifier of the optical receiver adjusts the power of the optical LO signal.

[0070] Although Figure 6 example blocks of process 600 are shown, in some implementations, process 600 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks compared to those shown. Additionally or alternatively, two or more blocks of process 600 may be executed in parallel. Figure 6

[0071] The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. Modifications and variations may be made in light of the above disclosure, or may be obtained from practice of the implementations. Additionally, any implementations described herein may be combined, unless the foregoing disclosure expressly provides a reason that one or more implementations cannot be combined.

[0072] As used herein, the term "component" is intended to be broadly construed as hardware, firmware, and / or a combination of hardware and software. Clearly, the systems and / or methods described herein may be implemented in different forms of hardware, firmware, or a combination of hardware and software. The actual specific control hardware or software code used to implement these systems and / or methods is not a limitation of these implementations. Accordingly, the operation and behavior of the systems and / or methods described herein are not referenced to a particular software code. It should be understood that software and hardware can be designed based on the description herein to implement the systems and / or methods.

[0073] As used herein, depending on the context, meeting a threshold may refer to a value that is greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, etc.

[0074] ​Even though particular combinations of features are recited in the claims and / or disclosed in the specification, these combinations are not intended to limit the disclosure of various implementations. In fact, many of these features can be combined in ways that are not specifically recited in the claims and / or not disclosed in the specification. Although each dependent claim listed below can directly depend on only one claim, the disclosure of various implementations includes the combination of each dependent claim with every other claim in the claim set. As used herein, a phrase that refers to "at least one" in a list of items means any combination of those items, including a single member. For example, "at least one of a, b, or c" is intended to cover a, b, c, a - b, a - c, b - c, and a - b - c, as well as any combination of multiple of the same items.

[0075] Unless explicitly described, an element, act, or instruction used herein should not be construed as critical or essential. Further, as used herein, the article "a" is intended to include one or more items and can be interchanged with "one or more". Further, as used herein, the article "the" is intended to include one or more items associated with the article "the" and can be interchanged with "the one or more". Further, as used herein, the term "set / group" is intended to include one or more items (e.g., related items, unrelated items, or a combination of related and unrelated items) and can be interchanged with "one or more". When only one item is intended, the phrase "only one" or similar language is used. Further, as used herein, the terms "has", "have", "possess", etc. are intended to be open - ended terms. Further, the phrase "based on" is intended to mean "at least partially based on" unless otherwise explicitly stated. Further, as used herein, the term "or" when used in series is intended to be inclusive and can be interchanged with "and / or" unless otherwise explicitly stated (e.g., if used in conjunction with "either" or "only one of").

Claims

1. An optical receiver, comprising: an optical amplifier connected to a local oscillator (LO); an optical amplifier controller connected to the optical amplifier; and a plurality of optical hybrid mixers of the optical receiver, wherein the optical amplifier is configured to: receive an optical LO signal from the LO; receive a voltage value associated with an optical input signal of the optical receiver; adjust the power of the optical LO signal based on the voltage value; and after adjusting the power of the optical LO signal, provide the optical LO signal to the plurality of optical hybrid mixers; wherein the optical amplifier controller is configured to: receive a control signal that is at least partially based on the optical input signal; based on the control signal, determine whether the optical amplifier controller is to control the optical amplifier using an automatic power control (APC) mode or an automatic gain control (AGC) mode; and based on the determination, send one of the following as the voltage value to the optical amplifier: a representative voltage value associated with the optical input signal when the optical amplifier controller is to control the optical amplifier using the APC mode, or a default voltage value associated with the optical input signal when the optical amplifier controller is to control the optical amplifier using the AGC mode.

2. The optical receiver according to claim 1, wherein the optical amplifier is a semiconductor optical amplifier.

3. The optical receiver according to claim 1, further comprising a loop controller, wherein the loop controller is configured to: receive a plurality of optical signal strength values associated with the optical input signal and the plurality of voltage values; process the plurality of optical signal strength values to determine a representative optical signal strength value; process the plurality of voltage values to determine the representative voltage value; and when the representative optical signal strength value does not meet an optical signal strength threshold, cause the representative voltage value to be provided to the optical amplifier as the voltage value.

4. The optical receiver according to claim 3, wherein the loop controller is configured, when causing the representative voltage value to be provided to the optical amplifier as the voltage value: generate a control signal indicating that the APC mode is to be used to control the optical receiver; and provide the control signal and the representative voltage value to the optical amplifier controller so that the optical amplifier controller provides the representative voltage value to the optical amplifier as the voltage value.

5. The optical receiver according to claim 1, further comprising a loop controller, wherein the loop controller is configured to: receive a plurality of optical signal strength values associated with the optical input signal; process the plurality of optical signal strength values to determine a representative optical signal strength value; and when the representative optical signal strength value meets the optical signal strength threshold, cause the default voltage value to be provided to the optical amplifier as the voltage value.

6. The optical receiver according to claim 5, wherein the loop controller is configured such that when the default voltage value is provided to the optical amplifier as the voltage value: Generate a control signal indicating that the AGC mode is to be used to control the optical receiver; and Provide the control signal to the optical amplifier controller so that the optical amplifier controller provides the default voltage value to the optical amplifier as the voltage value.

7. An optical receiver, comprising: An optical amplifier optically connected to a local oscillator (LO), An optical amplifier controller connected to the optical amplifier, and A plurality of optical hybrid mixers of the optical receiver, wherein the optical amplifier is configured to: Receive an optical LO signal from the LO, Receive a voltage value associated with the optical input signal of the optical receiver, Control the power of the optical LO signal based on the voltage value, and After adjusting the power of the optical LO signal, provide the optical LO signal to the plurality of optical hybrid mixers; And A controller configured to: Determine the voltage value associated with the optical input signal, where the voltage value is a representative voltage value associated with the optical input signal as the voltage value, or a default voltage value associated with the optical input signal; Based on the determination, generate a control signal indicating that one of an automatic power control (APC) mode or an automatic gain control (AGC) mode is to be used to control the optical receiver; And Provide the control signal to another controller of the optical receiver so that the another controller provides the representative voltage value or the default voltage value to the optical amplifier, Wherein when the control signal indicates that the APC mode is to be used to control the optical receiver, the another controller is caused to provide the representative voltage value to the optical amplifier; And when the control signal indicates that the AGC mode is to be used to control the optical receiver, the another controller is caused to provide the default voltage value to the optical amplifier.

8. The optical receiver according to claim 7, wherein the default voltage value is a representative peak voltage value associated with the optical input signal.

9. The optical receiver according to claim 7, wherein the controller is configured such that when determining the voltage value: Receive a plurality of peak voltage values associated with the optical input signal from a plurality of transimpedance amplifiers (TIAs) of the optical receiver; and Process the plurality of peak voltage values to determine the voltage value.

10. The optical receiver according to claim 7, wherein the controller is configured such that when determining the voltage value: Receive another control signal and a representative peak voltage value associated with the optical input signal from another controller; and Based on the another control signal, determine that the default voltage value is the representative peak voltage value.

11. The optical receiver according to claim 7, wherein the controller is configured such that when determining the voltage value: Receiving another control signal from another controller; and Based on the another control signal, determining that the voltage value is the default voltage value.

12. The optical receiver according to claim 7, wherein the default voltage value is a representative peak voltage value associated with the optical input signal, wherein the controller is configured to: Receive another control signal; Based on the another control signal, determining to use the APC mode to control the optical receiver; and Based on determining to use the APC mode to control the optical receiver, sending the voltage value to the optical amplifier.

13. The optical receiver according to claim 7, wherein the controller is configured to: Receive another control signal; Based on the another control signal, determining to use the AGC mode to control the optical receiver; and Based on determining to use the AGC mode to control the optical receiver, sending the voltage value to the optical amplifier.

14. A method for power control of an optical receiver, comprising: Receiving, by a controller of the optical receiver, a plurality of optical signal intensity values associated with an optical input signal from a plurality of transimpedance amplifiers (TIAs) of the optical receiver; Processing, by the controller, the plurality of optical signal intensity values to determine a representative optical signal intensity value; Determining, by the controller, whether the representative optical signal intensity value meets an optical signal intensity threshold; Generating, by the controller, a control signal based on determining whether the representative optical signal intensity value meets the optical signal intensity threshold, wherein when the representative optical signal intensity value meets the optical signal intensity threshold, the control signal indicates to use an automatic gain control (AGC) mode to control the optical receiver, or wherein when the representative optical signal intensity value does not meet the optical signal intensity threshold, the control signal indicates to use an automatic power control (APC) mode to control the optical receiver; and Adjusting, by the controller based on the control signal, the power of an optical local oscillator (LO) signal associated with the optical receiver, wherein adjusting the power of the optical LO signal includes: Providing the control signal to another component of the optical receiver to cause an optical amplifier of the optical receiver to adjust the power of the optical LO signal.

15. The method according to claim 14, wherein the another component includes an optical amplifier controller.

16. The method according to claim 14, wherein providing the control signal includes: Providing the control signal to the another component to cause the another component to provide a default voltage value to the optical amplifier.

17. The method according to claim 14, wherein providing the control signal includes: Providing the control signal to the another component to cause the another component to provide a representative peak voltage value to the optical amplifier.

18. The method according to claim 14, wherein the plurality of optical signal intensity values include a plurality of peak voltage values associated with the optical input signal.

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