System and method for optical signal generation

Abstract

The invention relates to a system and method for optical signal generation. An optical signal generation system for generating a multi-stage optical signal using binary keying includes an array of light sources, a control circuit, and an optical coupling mechanism. The system is operable to configure, using the control circuit, each light source in the array of light sources to a high state or a low state based on a received input signal to generate a plurality of light output signals. A plurality of optical output signals may be transmitted to an optical coupling mechanism and combined into a single optical signal to generate a multi-level output signal representative of the received input signal. The multi-stage output signal may include a pulse amplitude modulation (PAM) equivalent signal. The light source array may include a vertical cavity surface emitting laser (VCSEL), an edge emitting laser, or a light emitting diode (LED).

Description

Background Technology

[0001] Traditional optical modulation schemes, such as pulse amplitude modulation (PAM) and quadrature amplitude modulation (QAM), typically rely on linear modulation techniques that continuously adjust signal parameters within a specific range. While effective, these methods usually require complex and precise control systems to maintain signal integrity, especially at high data rates. A simpler, more cost-effective approach is needed that reduces reliance on precise analog control mechanisms without compromising the ability to meet ever-increasing bandwidth demands.

[0002] The subject matter of this disclosure aims to overcome or at least reduce the impact of one or more of the aforementioned problems. Summary of the Invention

[0003] This disclosure relates to the field of optical communications, and more specifically to modulation techniques for encoding and transmitting data over optical fibers or free space. In some examples, this disclosure introduces a novel method and system for generating optical signals that utilizes discrete amplitude modulation, alone or in combination, via binary high / low keying. Unlike traditional linear modulation techniques that require multi-level variations in signal parameters, this method employs binary switching to modulate optical signals, providing a simplified approach to achieving high data rates and efficient signal processing in optical communication systems.

[0004] Based on the disclosed examples, this disclosure presents a method and system for generating optical signals by employing binary high / low keying (binary switching mechanism) on the output amplitude of a light source, either individually or collaboratively. In some cases, this approach simplifies the generation and recovery process, enables efficient use of the spectrum, while promoting high data throughput and reducing the complexity of optical communication systems.

[0005] These and other features of this disclosure will become more apparent from the following description and appended claims.

[0006] The above description of the invention is not intended to summarize every potential implementation or aspect of this disclosure. Attached Figure Description

[0007] To further illustrate the foregoing and other features of this disclosure, the subject matter will be described in more detail by referring to specific examples of the disclosure shown in the accompanying drawings. It should be understood that these drawings depict only some examples of the subject matter and are therefore not to be construed as limiting its scope.

[0008] Figure 1 An example light source array for generating optical signals using binary keying is shown according to an example embodiment of the present disclosure.

[0009] Figure 2A schematic diagram of an example light source arrangement for binary keying according to an example embodiment of the present disclosure is shown.

[0010] Figure 3 The relative time relationship of the output of a combined light source array using only multiple elements in the array in a binary keying manner according to an exemplary embodiment of the present disclosure is shown.

[0011] Figure 4 A binary weighted light source array using binary keying is shown according to an example embodiment of the present disclosure.

[0012] Figure 5 The relative time relationship of binary-weighted light source output using binary keying according to an exemplary embodiment of this disclosure is shown.

[0013] Figure 6 A schematic diagram of an example light source arrangement having a photonic integrated circuit for binary keying is shown according to an example embodiment of the present disclosure.

[0014] Figure 7 A schematic diagram of an example edge-emitting laser arrangement having a photonic integrated circuit for binary keying is shown according to an example embodiment of the present disclosure.

[0015] Figure 8 This is a flowchart of a light source modulation process using binary keying according to an exemplary embodiment of the present disclosure.

[0016] Figure 9 Eye diagram modeling results of a single-laser PAM-4 system and a multi-laser binary keyed PAM-4 equivalent system according to exemplary embodiments of the present disclosure are shown.

[0017] The present invention is described more fully with reference to the accompanying drawings. These drawings may be merely schematic representations of current filters, components, facilities, or methods to enhance understanding of the disclosed concepts. Detailed Implementation

[0018] This paper discloses a laser array for generating multi-level signals by modulating lasers using binary keying. The laser array includes an optical transmitter comprising an array of lasers, control circuitry, and an optical coupling mechanism. The system is operable to configure each laser in the laser array to a high or low state based on a received input signal using the control circuitry to generate multiple optical output signals. These multiple optical output signals can be combined into a single optical signal by the optical coupling mechanism to generate a multi-level output signal representing the received input signal.

[0019] Switch to the attached image. Figure 1An example light source array for generating optical signals using binary keying is shown according to an exemplary embodiment of the present disclosure. (Refer to...) Figure 1 The diagram illustrates an optical communication system 100, which includes a light source array 101, a mirror 105, a lens 107, an optical fiber 109, a receiver 111, and a controller 113. In this example, the light source array includes three visible light sources 103A-103C, but any number of light sources can be used depending on the desired output level. In this example, three lasers can be used for PAM-4 or PAM-4 equivalent modulation, since the resulting PAM-4 equivalent signal is the same as the PAM-4 signal but with different generation methods. The markings of -1, 0, and +1 for the three light sources are merely an example of symmetrical placement, although this disclosure is not limited to this, as any orientation and placement is possible, for example, depending on the available space. It should be noted that in this example, the light sources can include VCSELs or LEDs, or any structure capable of emission from a structural surface.

[0020] In this example scenario, the four PAM levels are defined by each light source 103A-103C in either a high or low state, rather than by changing the light intensity of a single light source across multiple levels. Therefore, in one example, the PAM-4 equivalent modulation can be configured as low / low / low, low / high / low, low / high / high, and high / high / high, thus providing four distinct power levels without requiring precise analog control of any of the light sources 103A-103C to achieve these four different output levels. It should be noted that a low state for each light source does not imply zero current, but rather a value above the device's threshold current level, such as... Figure 1 As shown in the small diagram, this allows for improved switching speed. For example, low-state quiescent current can be increased to higher currents to increase bandwidth.

[0021] Each additional light source provides another level of output optical signal. For PAM-8 equivalent modulation, seven light sources can be used, arranged at the vertices and center of a hexagon, for example, as shown in the reference. Figure 2 As further illustrated. Furthermore, in any spatial configuration, any number of light sources is possible, including redundant light sources for the optical signal generation system.

[0022] The main advantage of this binary light source modulation and multi-stage signal generation scheme is the simplified signal generation. From the transmitter's perspective, the combined signal appears as a PAM signal without requiring a single light source to be configured at multiple levels, i.e., a PAM equivalent signal. By utilizing binary switching, the system reduces the need for complex control electronics and precise analog adjustments, while still being able to generate signals exceeding 100 GBaud. Furthermore, Figure 1The LI curve of the laser or LED source shown in the small figure illustrates another advantage of the binary amplitude modulation / signal generation scheme: any nonlinearity in the LI curve will not affect the operation because there is no need to accurately control the output at multiple current levels along the curve.

[0023] Light sources 103A-103C can generate optical signals in the infrared wavelength range, such as in the 850nm range. Although they can be used for optical communication purposes in the 1.3μm and / or 1.5μm range, other wavelength ranges are also possible. For example, light sources 103A-103C can be fabricated on a single substrate with heat dissipation capabilities and can include VCSELs, LEDs, micro-LEDs, backlit LCD panels, plasma, or OLEDs.

[0024] Figure 1 Also shown are a reflector 105, a lens 107, an optical fiber 109, a receiver 111, and a controller 113. The reflector 105 includes a reflective surface for redirecting various optical signals generated by the light sources 103A-103C to the lens 107. In the example shown, the reflector provides a 90-degree deflection for the optical signals from the light sources 103A-103C to the lens 107, although other angles are possible depending on the placement of downstream optics, and, for example, if the light is emitted directly into the optical fiber, a reflector may not be necessary.

[0025] To generate multi-level signals, lens 107 can focus the received optical signals 115A-115C onto a single core of fiber 109, thereby providing a simple optical coupling mechanism to combine multiple light source outputs into a single optical signal for communication via fiber 109 or free space transmission. Although Figure 1 A lens is shown, but lens 107 may also include multiple lenses depending on the focusing requirements of the received light beam. In another example embodiment, the mirror and lens may be combined into a single optical component, or the lens and mirror may be omitted depending on the direction of the light beam output from the light source.

[0026] The controller 113 may include circuitry for configuring the current entering the light sources 103A-103C, and therefore may include a processor and associated electronics for controlling the output current applied to the light sources 103A-103C. Although a single block is shown for the controller 113, several separate circuit blocks may be used, such as static bias circuitry and modulation high / low current circuitry for modulation.

[0027] Since the multi-level outputs are defined by the binary high / low conditions of the light sources 103A-103C, the complexity of the circuitry can be reduced compared to the control circuitry required to accurately control the current of multiple output levels and the associated settling time of each level. Because the controller 113 only needs to configure a high or low state, the linearity requirement of the light sources 103A-103C is reduced or eliminated. Therefore, the controller 113 can include digital circuitry for configuring high or low levels, eliminating the need for analog circuitry for controlling the output levels that change between high and low. For example, the present disclosure utilizing binary modulation eliminates the need for digital-to-analog converters (DACs) required in conventional PAM applications to configure the optical output into multiple intensity levels.

[0028] Receiver 111 may include circuitry for receiving optical signals and generating a demodulated signal representing the signal transmitted via optical fiber 109. Therefore, receiver 111 may include amplification, detection, and demodulation capabilities, for example, for generating electrical signals from one or more received optical signals.

[0029] In operation, an electrical data signal (Data signal In) can be transmitted to a controller 113, which in turn applies a digital signal to the light source array 101, converting each of the light sources 103A-103C to a high or low state, wherein these states are configured, for example, to generate four levels of PAM-4 equivalent modulation by accumulating high-frequency optical signals. Each optical signal 115A-115C is guided by a mirror 105 to a lens 107, wherein the focal length of the lens 107 focuses the light beam onto the input end face of the optical fiber 109. In another exemplary embodiment, the lens 107 can focus the optical signals 115A-115C directly onto the input of the receiver 111 via free-space communication.

[0030] As each of the optical signals 115A-115C is coupled into the core of fiber 109, the light intensity is accumulated, resulting in multiple possible levels defined by the binary states of each light source 103A-103C. In this way, the PAM-4 equivalent signal is transmitted to receiver 111 without requiring any light sources to be configured at multiple output levels, significantly reducing circuit complexity. Although this example shows a PAM-4 equivalent (i.e., it is the same as a PAM signal but with a different generation method), arbitrary level modulation can be utilized depending on the number of light sources.

[0031] Reducing the modulation depth decreases the variation in carrier density, leading to a reduction in the variation in refractive index within the cavity, such as reducing laser chirp. With reduced chirp, the spectral width of the emitted carriers narrows, accompanied by a decrease in pulse broadening over the transmission distance in the fiber. Although modal dispersion is primarily influenced by fiber modal characteristics and the initial modal distribution of the optical signal, reduced chirp helps maintain a narrower pulse width, indirectly mitigating / reducing intermodal interference that would be exacerbated by a wider spectral content. Reducing the modulation depth allows the laser to operate in a more linear region, which reduces nonlinear distortion generated by higher modulation depths, thereby improving the signal integrity of advanced modulation formats.

[0032] Figure 2 A schematic diagram of an example light source arrangement for binary keying according to an exemplary embodiment of the present disclosure is shown. (Refer to...) Figure 2 An array 201 of seven light sources 203A-203G is shown, wherein six lasers are arranged at the six corners of a hexagon and one laser is in the center. In this way, seven light sources 203A-203G can be used to generate a PAM-8 equivalent signal. In this way, an N-level signal can be generated by (N-1) light sources, where each light source is binary modulated. In another example implementation, some of the light sources 203A-203G can provide redundancy for lower-level modulation schemes, such as a PAM-4 equivalent scheme. Although... Figure 2 The diagram shows a symmetrical hexagonal array, but the invention is not limited thereto; for example, any orientation and placement are possible depending on space or heat dissipation requirements. The light source 203A-203G may include, for example, VCSELs, LEDs, micro-LEDs, backlit LCD panels, plasma, or OLEDs.

[0033] Figure 3 The diagram illustrates the relative time relationship of the output of a combined light source array using only binary keying of multiple elements in the array, according to an exemplary embodiment of this disclosure. In this example, the light source array includes a VCSEL, but as mentioned above, other light sources are also possible. Figure 300 illustrates the relationship between the normalized amplitude of the combined optical signal and time, for example... Figure 1 The optical signal intensity in fiber 109 and / or at receiver 111. Figure 3In one example, each of the four PAM-4 equivalent levels is labeled, where level 0 is configured with a low / low / low output level for each laser, level 1 with a low / low / high output level, level 2 with a high / high / low output level, and level 3 with a high / high / high output level. In another example, level 0 is configured with a low / low / low output level for each laser, level 1 with a low / high / low output level, level 2 with a low / high / high output level, and level 3 with a high / high / high output level. Other examples are also possible.

[0034] Figure 300 illustrates the PAM-4 equivalent signal, where only each laser in the array is configured with a high or low output level, eliminating the need for complex controller circuitry for multi-stage signaling. In conventional multi-stage modulation using a single laser, the laser and driver need to exhibit linearity and a high slew rate to reach full swing within a unit time interval. Using binary keying with equally weighted lasers, each laser can operate at a reduced slew rate (1 / 3 the value of a single laser).

[0035] Figure 4 A binary weighted light source array using binary keying is shown according to an example embodiment of the present disclosure. Figure 4 A binary weighted light source generation system 400 is shown, which includes light sources 403A and 403B, a reflector 405, a lens 407, a combiner 408, an optical fiber 409, a receiver 411, and a controller 413.

[0036] Light sources 403A and 403B can be used with reference Figure 1 The described light sources, including VCSELs and LEDs, are fundamentally similar but differ in their optical power and area, such as... Figure 4 The different radii R1 and R2 are shown. When the optical power of a VCSEL or LED is proportional to the optical output area, under the same conditions, in order to obtain twice the output of light source 403A emitted from light source 403B, R2 is sqrt(2) times larger than R1. Depending on the desired modulation scheme, this optical power in multiples of 2 can be extended to any number of light sources. Furthermore, although Figure 4 VCSELs are shown, but other light sources are also possible, such as PCSELs, edge-emitting lasers, light-emitting diodes (LEDs), micro-LEDs, backlit LCD panels, plasma, or OLEDs.

[0037] In another example scenario, the binary-weighted output intensity of the light sources in the array can be configured by the number of junctions in the light sources, where double the output power can be obtained by activating a laser or LED with two junctions compared to one junction. In yet another scenario, in instances where the same light source is desired, different output levels can be obtained by coating some of the lasers with neutral density filters, thus achieving multiple output levels while still only having binary high / low control.

[0038] In this exemplary embodiment, PAM-4 equivalent modulation is achieved using two binary weighted light sources 403A and 403B. The outputs 0, 1, 2, and 3 are configured via low / low, high / low, low / high, and high / high settings of the laser sources 403A and 403B, respectively, as configured via controller 413. (Refer to the above...) Figure 1 As described above, the circuitry in controller 413 can be significantly simplified compared to conventional PAM-4 or higher driver circuits that must accurately control multiple laser output levels. Furthermore, any number of light sources is possible, including redundant sources for a multi-stage optical generation system.

[0039] The reflector 405, lens 407, optical fiber 409, receiver 411, and controller 413 can be used with a reference. Figure 1 The described similarly named components are substantially similar, while the optional combiner 408 includes an optical coupling device for combining multiple received optical signals into a single output in instances where lens 407 cannot combine multiple input signals with different optical profiles into a single light spot (e.g., the core of fiber 409) or directly onto receiver 411. Furthermore, although Figure 4 A lens is shown, but lens 407 may also include multiple lenses depending on the focusing requirements of the received beam. In this example, combiner 408 may include multiple inputs for receiving optical signals generated by light sources 403A and 403B and a single output for transmitting the output optical signal to optical fiber 409 or alternatively via free space to receiver 411. Combiner 408 may include waveguide couplers, multiplexers, or other optical signal combiners.

[0040] In operation, the controller 413 can receive an input signal, "data signal input," and configure light sources 403A and 403B to a high or low state based on the received signal. The generated optical signals 415A and 415B are orthogonally reflected by mirror 405 and focused by lens 407 into combiner 408. This combiner combines optical signals 415A and 415B into a single optical signal for transmission to receiver 411 via optical fiber 409 or free-space communication. In receiver 411, the received modulation signal can be detected by a photodetector, thereby generating an electrical signal representing the data signal input used to modulate light sources 403A and 403B.

[0041] Figure 5 The diagram illustrates the relative time relationship of a binary-weighted laser output using binary keying according to an exemplary embodiment of this disclosure. (Refer to...) Figure 5 Figure 500 shows light intensity in arbitrary units on the Y-axis and time in seconds on the X-axis. The output from light source 403A is shown by the output signal labeled R1, and the output signal from light source 403B is shown by the output signal labeled R2. In this example, light sources 403A and 403B comprise VCSELs, although other types are also possible, such as LEDs, micro-LEDs, OLEDs, plasma sources, or backlit LCD panels. The relative intensity shows that the intensity of light source 403B is twice that of light source 403A. In this way, by configuring light sources 403A and 403B as low / low, high / low, low / high, and high / high, the two light sources can provide output levels of 0, 1, 2, and 3. Furthermore, any number of light sources is possible, including redundant light sources for a multi-level optical signal generation system.

[0042] In traditional multi-stage modulation using a single laser, the laser and driver need to exhibit linearity and a high slew rate to achieve full swing within a unit time interval. Using binary-weighted lasers or binary keying of LEDs, higher output sources can operate at a reduced slew rate (2 / 3 the value of a single source), while lower output sources can operate at 1 / 3 the slew rate of a single source. As the modulation depth decreases, the change in carrier density decreases, resulting in a reduction in the change in intracavity refractive index and chirp.

[0043] Figure 6 A schematic diagram of an example light source arrangement having a photonic integrated circuit for binary keying is shown according to an example embodiment of the present disclosure. Figure 6A binary keying optical system 600 is shown, which includes a light source array 601, light sources 603A-603C, a photonic integrated circuit (PIC) 605, an optical fiber 609, a receiver 611, and a controller 613. The light source array 601, light sources 603A-603C, optical fiber 609, receiver 611, and controller 613 can be connected to… Figure 1 and Figure 4 The components with similar names are generally similar, but in this example, PIC 605 is used to receive multiple optical signals from light sources 603A-603C and couple them to optical fiber 609, or alternatively, to couple optical signals to receiver 611 in free space. For example, light sources 603A-603C may include VCSELs, LEDs, micro-LEDs, OLEDs, plasma sources, or backlit LCD panels.

[0044] PIC 605 may include silicon or other materials used to manufacture the PIC, and may include multiple optical components for manipulating optical signals within the structure, with the aim of receiving multiple optical signals from light sources 603A-603C and coupling them to optical fiber 609, thereby providing an optical coupling mechanism for accumulating the optical signals. Therefore, PIC 605 may include an optical coupler for receiving optical signals from light sources 603A-603C. The optical coupler may include, for example, a grating coupler. Furthermore, PIC 605 may include waveguides for propagating the received optical signals to other optical components, such as one or more waveguide couplers for combining the optical signals into a single optical signal. Additionally, in instances where polarization control is desired in PIC 605, PIC 605 may include a polarization rotator.

[0045] The PIC 605 can be physically coupled to the light source array 601 to align the outputs of light sources 603A-603C with the optical couplers in the PIC 605 for efficient coupling of optical signals. Electrical interconnects, such as bump bonds, can be used to couple the light source array 601 to the PIC 605. Furthermore, any number of laser or LED sources are possible, including redundant light sources for the modulation system.

[0046] In operation, controller 613 can receive an input signal, "data signal input," and configure light sources 603A-603C to a high or low state based on the received signal. The generated optical signal is coupled to PIC 605, which combines the optical signals into a single optical signal for transmission to receiver 611 via optical fiber 609 or alternatively, free-space communication. Accumulation of the optical signal in PIC 605 enables multi-level data signals, such as PAM-4 equivalent or higher, where light sources 603A-603C are only biased to a high or low state without requiring precise voltage control of multiple output levels. In receiver 611, the received modulation signal can be detected by a photodetector, thereby generating an electrical signal representing the data signal input used to modulate light sources 603A-603C.

[0047] Figure 7 A schematic diagram of an example edge-emitting laser arrangement having a photonic integrated circuit for binary keying, according to an exemplary embodiment of the present disclosure, is shown. (Refer to...) Figure 7 The diagram illustrates a binary keying optical system 700, which includes a laser array 701, a PIC 705, an optical fiber 709, a receiver 711, a controller 613, and a substrate 721. The PIC 705, optical fiber 709, receiver 711, and controller 713 can be coupled with… Figure 1 , Figure 4 and Figure 6 The components with similar names are essentially similar, but in this example, laser array 701 is an array of edge-emitting lasers whose output signals are horizontally coupled to PIC 705. In another example scenario, laser array 701 may include multiple discrete lasers, each a separate chip. Furthermore, instead of PIC 705, lenses or lens assemblies can be used to couple optical signals from laser array 701 to optical fiber 709, or alternatively, to a receiver via free space.

[0048] Substrate 721 may include a semiconductor or ceramic substrate, on which laser array 701 and PIC 705 may be bonded to achieve a fixed and accurate alignment between laser array 701 and PIC 705. In one example scenario, substrate 721 may include a semiconductor substrate having circuitry for controller 713. Laser array 701 may include a plurality of edge-emitting semiconductor lasers operable to emit an array of optical signals 715 directed to PIC 705.

[0049] The lasers in laser array 701 can be configured to a high or low state based on data signal input via controller 713. Furthermore, any number of laser sources are possible, including redundant lasers for the modulation system.

[0050] The PIC 705 may include an array of optical couplers for receiving optical signals 715, and multiple waveguides and optical couplers for combining multiple optical signals 715 into a single optical signal for transmission via optical fiber. This accumulation of binary keyed optical signals enables multi-level modulation schemes without requiring precise multi-level output control of the lasers in the laser array 701.

[0051] In operation, controller 713 receives an input signal, "data signal input," and configures the lasers in laser array 701 to a high or low state based on the received signal. The generated optical signal 715 is coupled to PIC 705, which combines the optical signals into a single optical signal for transmission to receiver 711 via fiber optic cable 709 or alternatively, free-space communication. Accumulation of the optical signals in PIC 705 enables multi-level data signals, such as PAM-4 equivalent or higher, while the lasers in laser array 701 are only biased to a high or low state, without requiring precise voltage control of multiple output levels. In receiver 711, the received modulation signal can be detected by a photodetector, thereby generating an electrical signal representing the data signal input used to modulate laser array 701.

[0052] Figure 8 This is a flowchart of a light source modulation process using binary keying according to an exemplary embodiment of this disclosure. (Refer to...) Figure 8 The diagram illustrates a binary keying modulation process 800 for a light source. This process begins in step 801, where input electrical data signals are received in light source control circuits 113, 413, 613, and 713. These control circuits are configured in step 803 to bias light sources 103A-103C, 403A / 403B, and 603A-603C of light source arrays 101, 601, and 701 to a high or low state. In step 805, the optical signals are combined / accumulated into a single optical signal via an optical coupling element, by focusing the optical signal onto the same point of the waveguide in step 805, or by directly transmitting the optical signal to the same point on a detector in a remote receiver via free space. In step 807, the receiver extracts an output electrical signal based on the received optical signal.

[0053] Figure 9 Eye diagram modeling results for a single-laser PAM-4 system and a multi-laser binary keyed PAM-4 equivalent system according to exemplary embodiments of this disclosure are shown. (Refer to...) Figure 9 The diagram shows an eye diagram 900 for a conventional single-laser PAM-4 and an eye diagram 920 for a multi-laser binary keyed PAM-4 equivalent system. The frequency response 930 of the VCSEL for different bias currents (ranging from 2 mA to 10 mA in 1 mA increments) is also shown. As a comparison of the 2 mA and 10 mA curves shows, the lower current frequency response curve exhibits a lower bandwidth, while the higher current curve shows a flatter curve and a higher bandwidth.

[0054] In addition to reduced bandwidth, VCSELs also exhibit significant resonance at lower bias currents. When a VCSEL operates in PAM-n mode, there are n distinct states, each of which can transition from its current state to any other state. The bandwidth associated with these transitions depends on the transition from the current state to the next state, thus increasing as the transitions become larger, as implemented in the binary keying system disclosed herein. Furthermore, this dependence on the transition size leads to increased inter-symbol interference (ISI) and eye skew, and resonance in the frequency response causes ringing and contributes to ISI.

[0055] Figure 9 The VCSEL frequency response shown is modeled based on VCSEL laser physics involving rate equations that describe the dynamic behavior of carrier and photon densities within the laser cavity. The VCSEL rate equations comprise two coupled differential equations for carrier density and photon density. These equations collectively capture the interactions between electric pumping, photon generation and loss, and the laser output under different operating conditions. In this example, the VCSEL has a 3 dB corner frequency of 32 GHz at full bias, and the bandwidth decreases to approximately 22 GHz at the lowest operating bias. A 50 Gbaud input data signal with 5 ps (picosecond) rise and fall times is utilized in the model.

[0056] The eye pattern 900 of each individual VCSEL modulated into the PAM-4 states shows an eye diagram skew in the time dimension, as indicated by the dashed line, showing a skew of approximately 3 ps, and unequal eye diagram openings in the VCSEL output. Both are attributed to the change in VCSEL bandwidth as the input transitions from one state to another. In conventional PAM laser modulation, these effects require compensation through complex digital signal processing and become more pronounced with increasing baud rate relative to VCSEL bandwidth.

[0057] Eye pattern 920 illustrates the same 50 Gbaud input applied to a configuration of three VCSELs, where each VCSEL operates in only two states (high and low), and the output shown is the sum of the outputs of all three VCSELs. Due to the high bias and only two states, all VCSELs maintain constant and high bandwidth. As shown in eye pattern 920, there is approximately zero (<0.5 ps) skew and equal eye diagram opening for all states and transitions. Therefore, complex and power-intensive digital signal processing is not required.

[0058] Another advantage of the disclosed multi-source binary keying modulation scheme is that operating three VCSELs, edge-emitting lasers, or LEDs in synchronous NRZ mode enables three times the power of a single source in PAM-4, which improves the optical signal-to-noise ratio. Furthermore, the constant bandwidth with a single ON-state output level reduces ISI and improves the bit error rate (BER), which eliminates the need for forward error correction (FEC) and its associated hardware requirements and latency overhead.

[0059] In the disclosed example, the optical communication system includes a light source array, control circuitry, and an optical coupling mechanism. The system is operable to configure each light source in the light source array to a high or low state based on a received input signal, using the control circuitry, to generate multiple optical output signals. While the light sources are biased to high and low states, it is understood that leading and trailing edge manipulation may occur for compensation purposes. The multiple optical output signals can be transmitted to the optical coupling mechanism and combined into a single optical signal to generate a multi-stage output signal representing the received input signal. This multi-stage output signal can simulate the output of a single light source modulated to each output stage, but with enhanced performance.

[0060] Multi-stage output signals can be transmitted to a receiver. These signals may include pulse amplitude modulation (PAM) equivalent modulated signals, as they are identical to typical PAM signals but generated by different means involving multiple sources. The light source array may include vertical-cavity surface-emitting lasers (VCSELs), edge-emitting lasers, light-emitting diodes (LEDs), plasma sources, or backlit LCDs. The high-state output levels of each light source may be binary-weighted relative to another light source in the array, where the light output area of ​​each light source is twice that of the other light source in the array. Optical coupling mechanisms may include lenses or photonic integrated circuits (PICs). PICs may include waveguide couplers. The light source array may be bonded to a PIC or may be laterally adjacent to a PIC.

[0061] In another example implementation, all light sources may have the same maximum power, wherein each light source is modulated to its maximum power, and the output signals from each light source are combined to generate multiple output power levels from the system. In another example, all light sources have the same maximum power, but each light source is modulated to a different power level. In this case, it is not necessary to combine the output signals, eliminating the need to combine the optics disclosed above.

[0062] In yet another example implementation, each light source can have a different maximum power level, wherein each light source is modulated to its maximum power, and it is not necessary to combine the optical signals to generate multiple levels of signals. Finally, each light source can have a different maximum power, and each light source is modulated to its maximum power and then combined to generate multiple output power levels. Therefore, this allows the use of the same or different VCSELs or other lasers or LED structures depending on factors such as chip size limitations, power requirements, manufacturing cost considerations, and design complexity.

[0063] In an example implementation, a multi-level optical signal generation system may include a light source array and control circuitry, wherein the system is operable to generate a multi-amplitude optical signal based on a received input signal by individually configuring each of the light sources in the light source array to a high state or a low state using the control circuitry, wherein the high state is different for each of the light sources in the array.

[0064] In another example implementation, a method for generating multi-level optical signals may include a light source array and a control circuit, which generates multi-amplitude optical signals by individually configuring each of the light sources in the light source array to a high state or a low state using the control circuit based on a received input signal, wherein the high state is different for each of the light sources in the array.

[0065] In the accompanying drawings, similar features are always indicated by the same or similar reference numerals.

[0066] The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concept conceived by the applicant. With the benefit of this disclosure, it will be understood that the foregoing features of any embodiment or aspect of the disclosed subject matter may be utilized alone or in combination with any other described features in any other embodiment or aspect of the disclosed subject matter.

Claims

1. A system for generating optical signals, the system comprising: Light source array; Control circuit; as well as Optical coupling mechanism, the system is operable as follows: Based on the received input signal, the control circuit is used to individually configure each of the light sources in the light source array to a high state or a low state to generate multiple light output signals. as well as The optical coupling mechanism is used to couple and combine the plurality of optical output signals into a single optical signal, thereby generating a multi-amplitude output signal representing the received input signal.

2. The system according to claim 1, wherein, The multi-stage output signal includes a pulse amplitude modulation equivalent signal.

3. The system according to claim 1, wherein, The light source array includes a vertical cavity surface-emitting laser.

4. The system according to claim 1, wherein, The light source high state of each light source is binary weighted relative to another light source in the light source array, wherein the light output area of ​​each light source is twice that of another light source in the light source array.

5. The system according to claim 1, wherein, The light source array includes edge-emitting lasers.

6. The system according to claim 1, wherein, The light source array includes light-emitting diodes.

7. The system according to claim 1, wherein, The optical coupling mechanism includes one or more lenses.

8. The system according to claim 1, wherein, The optical coupling mechanism includes a photonic integrated circuit.

9. The system according to claim 8, wherein, The photonic integrated circuit includes a waveguide coupler.

10. The system according to claim 8, wherein, The light source array is bonded to the photonic integrated circuit.

11. The system according to claim 8, wherein, The light source array is laterally adjacent to the photonic integrated circuit.

12. The system according to claim 1, wherein, A subset of the light source array provides redundancy for the other light sources in the light source array.

13. A method for generating an optical signal, the method comprising: In a light source generation system that includes a light source array, an optical coupling mechanism, and a control circuit: Based on the received input signal, the control circuit is used to configure each of the light sources in the light source array to a high state or a low state to generate multiple light output signals. The optical coupling mechanism is used to couple and combine the plurality of optical output signals into a single optical signal, thereby generating a multi-amplitude output signal representing the received input signal.

14. The method according to claim 13, wherein, The multi-stage output signal includes a pulse amplitude modulation equivalent signal.

15. The method according to claim 13, wherein, The light source array includes a vertical cavity surface-emitting laser.

16. The method according to claim 13, wherein, The light source high state of each light source in the light source array is binary weighted relative to another light source in the light source array, wherein the light output area of ​​each light source is twice that of another light source in the light source array.

17. The method according to claim 13, wherein, The light source array includes edge-emitting lasers.

18. The method according to claim 13, wherein, The light source array includes light-emitting diodes.

19. The method according to claim 13, wherein, The optical coupling mechanism includes one or more lenses.

20. The method according to claim 13, wherein, The optical coupling mechanism includes a photonic integrated circuit.

21. The method according to claim 20, wherein, The photonic integrated circuit includes a waveguide coupler.

22. The method according to claim 20, wherein, The light source array is bonded to the photonic integrated circuit.

23. The method of claim 20, wherein, The light source array is laterally adjacent to the photonic integrated circuit.

24. The method according to claim 13, wherein, A subset of the light source array provides redundancy for the other light sources in the light source array.

25. A system for generating optical signals, the system comprising: The system includes a light source array and a control circuit, which is operable to generate multi-amplitude optical signals based on received input signals by individually configuring each of the light sources in the light source array to a high or low state using the control circuit, wherein the high state is different for each of the light sources in the array.

26. A method for generating an optical signal, the method comprising: In a light generation system comprising a light source array and control circuitry: based on a received input signal, the control circuitry configures each of the light sources in the light source array to a high or low state to generate a multi-amplitude light signal, wherein the high state is different for each of the light sources in the array.

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