Method for reducing standby power consumption in optical wireless communication system

Abstract

An optical transmitter (100) comprises: a light source (210) configured to emit light for optical wireless communication based on an input signal comprising a data signal to be transmitted via the optical transmitter (100); a power switch (220) configured to turn on or off power to the light source (210); a detector (230) configured to: detect an input signal on a signal path of the optical transmitter (100); and transmit a first trigger signal related to transmission start SoT of the input signal to the switch controller (240); a switch controller (240) configured to control the power switch (220) to power on the light source (210) upon receiving the first trigger signal; wherein the optical transmitter (100) is configured to: prevent transmission of the data signal during a first time interval after power-on of the light source (210); and transmitting the data signal during a second time interval subsequent to the first time interval; wherein the first time interval is determined based on a settling time of the light source (210).

Description

Technical Field

[0001] The present invention relates to the field of optical wireless communications, such as Li-Fi communications. More particularly, various devices, systems and methods are disclosed herein that relate to reducing standby power consumption in optical wireless communication systems. Background Art

[0002] To enable more and more electronic devices (like laptops, tablets and smartphones) to connect wirelessly to the Internet, wireless communications face unprecedented demands on data rates and link quality, and this demand grows year after year in view of the emerging digital revolution involving the Internet of Things (IoT). Radio frequency technologies (like Wi-Fi) have limited spectrum capacity to embrace this revolution.

[0003] Meanwhile, optical wireless communications (OWC) have attracted increasing attention due to their inherent security enhancements and ability to support higher data rates over available bandwidths in the visible, ultraviolet (UV) and infrared (IR) spectrums. For example, depending on the wavelength used, this technology may also be referred to as coded light, light fidelity (LiFi), visible light communications (VLC) or free space optics (FSO). OWC or Li-Fi is directional and shielded by light-blocking materials, which offers the potential to deploy a larger number of access points in densely populated areas by spatially reusing the same bandwidth compared to Wi-Fi. These key advantages over wireless RF communications make OWC or Li-Fi a promising secure solution to relieve the pressure on the crowded radio spectrum for IoT applications and indoor wireless access. Other possible benefits of Li-Fi may include guaranteed bandwidth for a certain user and the ability to operate safely in areas that are otherwise susceptible to electromagnetic interference. Therefore, Li-Fi is a very promising technology that can enable the next generation of immersive connectivity.

[0004] WO2022008240A1 relates to a trigger-based optical wireless communication system, such that in order to establish a high-speed optical link, the endpoint device first sends an optical trigger signal to the access point in a low-power state. Only when a valid trigger signal is recognized after detecting the optical trigger signal, the access point switches to a normal operating state. Summary of the invention

[0005] To reduce power consumption, it is desirable to keep portions of the optical transmitter (such as the optical front end) in a sleep mode when there is no transmission. This can be achieved by observing the signal level of the incoming signal to be transmitted at the cable interface. The power savings are beneficial to both battery-powered end devices / terminals and ceiling-mounted optical access points.

[0006] In view of the above, the present disclosure relates to methods, apparatus and systems for providing improved uplink communication in an optical wireless communication system. More particularly, the object of the present invention is achieved by a method for allocating uplink radio resources as claimed in claim 1, by an optical access point as claimed in claim 11 and by a computer program as claimed in claim 15.

[0007] According to a first aspect of the present invention, an optical transmitter is provided. The optical transmitter is configured to transmit a data signal for optical wireless communication, and the optical transmitter includes: a light source configured to transmit light for optical wireless communication based on an input signal including a data signal to be transmitted via the optical transmitter; a power switch configured to turn on or off power to the light source; a detector configured to: detect an input signal on a signal path of the optical transmitter; and send a first trigger signal related to a transmission start SoT of the input signal to a switch controller; the switch controller is configured to control the power switch to power on the light source upon receiving the first trigger signal. The optical transmitter is configured to prevent transmission of a data signal during a first time interval after powering on the light source; and transmit a data signal during a second time interval subsequent to the first time interval; wherein the first time interval is determined based on a stabilization time of the light source.

[0008] Optical wireless communication can be implemented in the visible, ultraviolet (UV) and infrared (IR) light spectra. Therefore, optical wireless communication can also be referred to as Li-Fi communication or visible light communication (VLC). The light source or light emitter can be a light emitting diode (LED).

[0009] Since the light source is the largest power consuming component in an optical transmitter, it is desirable to keep the light source in an off state or in a sleep state as long as possible, so that the light source is powered only when transmitting. However, depending on the type of light source used, there is usually a delay, or so-called stabilization time, from powering up to entering a stable state for communication.

[0010] The stabilization time is the delay required for the optical source to settle to an output level suitable for optical wireless communication after power is applied. It is important to avoid transmitting data signals during the stabilization time. Otherwise, the remote receiving device will not be able to detect parts of the data signal because the output power of the optical transmitter is simply too low to support the link.

[0011] The detector is used to observe the input signal and provide a trigger signal to the switch controller early before the data signal actually arrives at the light source input. And then, the situation where the data signal is emitted by the light source during the stabilization time is avoided.

[0012] The optical transmitter can be a standalone device or integrated into another electronic device such as a laptop, tablet, smartphone, TV, display device, lamp, etc. The optical transmitter can also be deployed as an end device / terminal or an optical access point for providing connectivity to multiple end devices.

[0013] Advantageously, the detector is configured to observe an average signal strength of the input signal on the signal path within a time window and to detect the SoT when the average signal strength is above a predefined threshold.

[0014] Observing the average signal strength change from a low signal level to a high signal level and remain high for a certain duration usually triggers a SoT event.

[0015] Preferably, the detector is further configured to detect the end of transmission EoT of the input signal on the signal path; and send a second trigger signal related to EoT to the switch controller; and the switch controller is configured to control the power switch to cut off the power of the light source after a certain delay when receiving the second trigger signal, and the certain delay is at least equal to the propagation delay of the input signal from the detector to the light source.

[0016] This EoT detection can also be achieved by observing the input signal over a large enough time window to make a robust decision. A change from a high signal level to a low signal level and remaining low for a certain duration usually triggers an EoT event.

[0017] Alternatively, the switch controller is configured to control the power switch to de-energize the light source after a predefined maximum packet duration upon receiving the first trigger signal.

[0018] The predefined maximum packet duration may be determined according to a maximum packet duration defined in a certain optical wireless communication protocol or standard or another proprietary protocol related to a certain application.

[0019] Optionally, the predefined maximum packet duration is determined by taking into account an additional delay on top of any protocol or standard.The additional delay may at least cover the stabilization time of the light source.

[0020] In one option, a power switch is placed at the output of the light source driver.

[0021] Advantageously, the optical transmitter is configured to extend the packet to be transmitted by adding an additional field at the beginning of the packet; wherein the duration of the additional field is determined according to the first time interval, and to send the extended packet as an input signal to the optical source.

[0022] The additional field may include a predefined data pattern, such as a repeated preamble of a packet. The additional field may also simply include some dummy data.

[0023] By modifying the packet to be transmitted as a physical layer extension, power switch control is allowed without the need for a signal interface, so that the light source will be in a ready state before the actual data packet starts. In this way, the input signal is either an extended packet including a data signal, or an actual data packet to be transmitted.

[0024] Advantageously, the optical transmitter further comprises a signal interface configured to add an additional delay in a signal path of the optical transmitter before the light source; wherein the additional delay is determined according to the first time interval.

[0025] Preferably, a signal interface is added to the signal path after the point on the signal path detected by the detector and before the light source. In this sense, the switch controller will be able to generate a trigger signal before the actual data propagates to the light source. The additional delay is set according to a first time interval, which is ultimately determined by the stabilization time of the light source.

[0026] With this option, the input signal can be a conventional data packet and be identical to the data signal to be transmitted.Thus, the disclosed optical transmitter can include or be used in conjunction with a conventional modem chip for optical wireless communications.

[0027] Advantageously, the optical transmitter further comprises an amplifier connected between the signal interface and the light source.

[0028] The transmission chain may include an amplifier in front of the light source. The amplifier may also be a pulse amplifier for modulating the signal. For example, during transmission, the optical transmitter converts an electrical signal into an optical signal by modulating an input signal as input to the light source. This can be achieved by varying the output current of the pulse amplifier according to the input signal, which is then provided as input to the light source.

[0029] In one option, the signal interface is a delay unit.

[0030] As an example, an all-pass filter may be employed as a delay unit, which introduces a predefined amount of delay into the data path.

[0031] In another option, the signal interface is an analog signal multiplexer.

[0032] For example, a delay may be introduced into the signal path by using a multiplexer to keep the amplifier input at zero level for a first time interval determined based on the settling time of the light source and then connected to the incoming input signal for modulating the LED light level.

[0033] Advantageously, the data signal is modulated according to intensity modulation.

[0034] Intensity modulation (IM) is a type of modulation in which the optical power output of a light source varies depending on the data signal to be transmitted. Signals with intensity modulation are usually recovered by direct detection.

[0035] Intensity modulation and direct detection (IM / DD) is a cost-effective optical communication strategy that is widely used in fiber-optic communications, free-space optics communications, and indoor visible light communications.

[0036] In another example, the data signal may also be modulated according to an Orthogonal Frequency Division Multiplexing (OFDM) scheme.

[0037] OFDM as a digital multi-carrier modulation method is widely used in many communication systems because of its great robustness against harsh channel conditions (such as narrowband interference or frequency selective fading). By dividing the entire frequency band into multiple subcarriers, the system also has the flexibility to apply different modulation and coding schemes to each subcarrier, which can be used to maximize the capacity of the channel. For optical wireless communications, single-pole OFDM modulation techniques such as ACO-OFDM, DCO-OFDM, ADO-OFDM and / or flipped OFDM are usually used.

[0038] According to a second aspect of the present invention, an optical front end is provided. The optical front end is configured to transmit a data signal for optical wireless communication, and the optical front end includes: a light source configured to emit light for optical wireless communication based on an input signal including a data signal to be transmitted via the optical front end; a power switch configured to turn on or off the power to the light source; a detector configured to: detect the input signal on the signal path of the optical front end; and send a first trigger signal related to the transmission start SoT of the input signal to a switch controller; the switch controller is configured to control the power switch to power on the light source upon receiving the first trigger signal; and a signal interface configured to add an additional delay in the signal path before the light source; wherein the additional delay is determined according to the stabilization time of the light source.

[0039] The signal interface can be a delay unit or an analog signal multiplexer.

[0040] Preferably, a signal interface is added to the signal path after the point on the signal path detected by the detector and before the light source.

[0041] It provides a complete solution to the stabilization time problem of the light source at power-up, using a signal interface deployed in an optical front end (OFE). In this way, the input signal to the OFE can be a conventional data packet and is identical to the data signal to be transmitted. Therefore, the disclosed OFE can be used in conjunction with a conventional modem chip for optical wireless communications.

[0042] In another example, a system for optical communication includes an optical front end and a modem. The optical front end includes: a light source configured to emit light for optical wireless communication based on an input signal to be transmitted via the optical front end; a power switch configured to turn on or off power to the light source; a detector configured to: detect the input signal on the signal path of the optical front end; and send a first trigger signal related to the start of transmission SoT of the input signal to a switch controller; the switch controller is configured to control the power switch to power on the light source upon receiving the first trigger signal. The modem is configured to extend the packet to be transmitted by adding an additional field at the beginning of the packet; wherein the duration of the additional field is determined according to the stabilization time of the light source of the optical front end, and the extended packet is sent to the optical front end as an input signal.

[0043] Therefore, in this option, the optical front end does not have to contain a special signal interface to introduce additional delay in the signal path to compensate for the effect of light source stabilization. Instead, the modem provides additional fields or dummy data to the input signal in front of the actual data signal / packet to be transmitted. Therefore, data packet transmission will not be impaired due to slow stabilization of the light source.

[0044] According to another aspect of the present invention, a method for reducing standby power consumption is provided. A method for reducing standby power consumption in an optical transmitter, wherein the optical transmitter (100) is configured to transmit a data signal for optical wireless communication; the method comprises the steps of: the optical transmitter: based on an input signal including a data signal to be transmitted via the optical transmitter, emitting light for optical wireless communication by a light source; turning on or off power to the light source by a power switch; detecting the input signal on a signal path of the optical transmitter; sending a first trigger signal related to a start of transmission SoT of the input signal to a switch controller; controlling the power switch to power on the light source upon receiving the first trigger signal; preventing transmission of the data signal during a first time interval after the light source is powered on; and transmitting the data signal during a second time interval subsequent to the first time interval; wherein the first time interval is determined based on a stabilization time of the light source.

[0045] Advantageously, the method further comprises the steps of: detecting the end of transmission EoT of the input signal on the signal path; sending a second trigger signal related to the EoT to the switch controller; and upon receiving the second trigger signal, controlling the power switch to turn off the light source after a certain delay, and the certain delay is at least equal to the propagation delay of the data signal from the detector to the light source.

[0046] Alternatively, the method further comprises the step of controlling the power switch to de-energize the light source after a predefined maximum packet duration upon receiving the first trigger signal.

[0047] The predefined maximum packet duration may be determined according to a maximum packet duration defined in a certain optical wireless communication protocol or standard or another proprietary protocol related to a certain application.

[0048] Optionally, the predefined maximum packet duration is determined by taking into account an additional delay on top of any protocol or standard. The additional delay covers at least the stabilization time of the light source. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In the drawings, similar reference numerals are used throughout the different Figure 1 Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

[0050] Figure 1 shows a block diagram of an optical transmitter;

[0051] Figure 2 shows a block diagram of an optical front end;

[0052] Figure 3 An example of an optical transmitter is shown;

[0053] Figure 4 An example of a packet structure of an input signal is illustrated;

[0054] Figure 5 A block diagram of a system for OWC is shown; and

[0055] Figure 6 A flow chart of a method for an optical transmitter is shown. DETAILED DESCRIPTION

[0056] The embodiments set forth below represent information that enables those skilled in the art to practice these embodiments. When reading the following description according to the attached drawings, those skilled in the art will understand the concepts of the present disclosure and will recognize the applications of these concepts that are not particularly proposed in this article. It should be understood that these concepts and applications fall within the scope of the present disclosure.

[0057] The present invention relates to optical wireless communications (OWC) such as LiFi, which is being developed to enhance Wi-Fi and other RF communication technologies. In Li-Fi, information is typically transferred by modulating the intensity of light of a specific wavelength that illuminates a given area. OWC links are implemented using transceivers that conform to the selected wavelength and are capable of modulating / demodulating and encoding / decoding signals.

[0058] One of the key aspects of LiFi communication system is the power consumption of OFE. First, the transmitter part consumes a considerable amount of power (several Watts) in order to generate a sufficient signal-to-noise ratio (SNR) on the receiver side in order to obtain a good data throughput (100Mb / s or more). If LiFi communication is combined with normal lighting, the transmission power requirement can be ignored.

[0059] However, due to the slow modulation speed of LEDs used in normal lighting and the difficulty of integrating data modulators with LED drivers, normal practice is to use separate communication LED units, primarily at infrared (IR) wavelengths. While this separation has the added advantage of not requiring normal lighting to be active for data communication purposes, it increases overall power consumption. As standby power is becoming an issue of concern, especially in relation to lighting networks, it is of interest to investigate methods to address this issue.

[0060] A typical LiFi communication system may have several optical front ends (OFEs) that implement transceiver functionality by interfacing the optical and electrical signal transmission domains. Ceiling OFEs can act as distributed access points (AP1…APn), each covering a portion of the scene. Mobile endpoint OFEs (EPs) represent the interface device on the user side of the LiFi link, with a field of view covering at least one AP. The APs can be connected to the modem and network interface using copper or fiber optic connections.

[0061] Figure 1 A block diagram of an optical transmitter 100 is shown. As a basic setup, the optical transmitter 100 includes a light source 210, a power switch 220, a detector 230, and a switch controller 240. The light source 210 is configured to emit light for optical wireless communication based on an input signal including a data signal to be transmitted via the optical transmitter 100. The power switch 220 is configured to turn on or off the power to the light source 210. The detector 230 is configured to detect the input signal on the signal path of the optical transmitter 100 and send a first trigger signal related to the start of transmission (SoT) of the input signal to the switch controller 240. The switch controller 240 is configured to control the power switch 220 to power on the light source 210 upon receiving the first trigger signal. The optical transmitter 100 is configured to prevent the transmission of the data signal during a first time interval after the light source 210 is powered on; and transmit the data signal during a second time interval subsequent to the first time interval. The first time interval is determined based on the stabilization time of the light source 210.

[0062] The light source 210 is the component with the largest power consumption in the optical transmitter 100, and therefore from the viewpoint of power efficiency, it is important to keep the light source 210 in sleep mode as long as possible. However, due to the delay required for the light source 210 to stabilize at an output level suitable for optical wireless communication from power-on, a mechanism is needed to allow the light source 210 to stabilize before the actual data signal arrives. The detector 230 and the switch controller 240 are used to achieve this purpose. The detector 230 detects the input signal on the signal path at a point in front of the light source 210, and thus notifies the switch controller 240 to control the power switch 220 accordingly. In this way, when the light source 210 has stabilized, the actual data signal arrives at the light source 210, which allows the data signal to be transmitted at a suitable output level of the light source.

[0063] Figure 2 A block diagram of an optical front end 200 is shown. The optical front end 200 includes a light source 210, a power switch 220, a detector 230, a switch controller 240, and a signal interface 250. The light source 210 is configured to emit light for optical wireless communication based on an input signal including a data signal to be transmitted via the optical front end 200. The power switch 220 is configured to turn on or off power to the light source 210. The detector 230 is configured to detect an input signal on a signal path of the optical front end 200; and send a first trigger signal related to a start of transmission (SoT) of the input signal to the switch controller 240. The switch controller 240 is configured to control the power switch 220 to power on the light source 210 upon receiving the first trigger signal. The signal interface 250 is configured to add an additional delay in a signal path before the light source 210; wherein the additional delay is determined according to a stabilization time of the light source 210.

[0064] By deploying the signal interface 250 in the optical front end (OFE), the problem of stabilization time due to the power-on of the light source is completely solved inside the OFE. The input signal to the OFE can be a normal data packet and is the same as the data signal to be transmitted. Therefore, the disclosed OFE can be used in conjunction with a traditional modem chip for OWC.

[0065] Figure 3An implementation example of an optical front end (OFE) 200 is shown. In this example, during transmission, the OFE 200 modulates the LED current (ILED) by varying the output current (IMOD) of the pulse amplifier 260 according to the input signal, thereby converting the electrical signal into an optical signal. A power switch (PS) 220 is introduced on the LED supply line VCUP to switch off the light generation when there is no data transmission and thereby reduce the associated power consumption. The power switch 220 is driven by a switch controller (SC) 240 triggered by a detector 230, which is used to detect the start of transmission (SoT) and / or the end of transmission (EoT). A signal interface unit (SI) 250 is introduced to provide a predefined interval to allow the LED 210 to stabilize at an average output level, which will be used by the receiving optical front end OFE to establish a reference DC level for decoding OFDM modulation. In order to reduce the stabilization time of the LED driver 215, the power switch 220 is placed at the output so that when the signal to be transmitted arrives, the driver 215 starts in a state close to the normal transmission mode. Placing the power switch 220 at the input of the LED driver 215 will result in the loss of internal state (e.g., discharge of a capacitor), resulting in a long startup time. Although the pulse amplifier 260 sinks or sources large IMOD currents during data transmission, its bias current during standby mode may be low and may not need to be shut down.

[0066] For signals modulated with OFDM, the various carrier signals are amplitude modulated according to the assigned data bits. Since the signal levels before the start of transmission and during transmission are distinguishable, a comparator with an appropriate threshold can be used to detect the start of transmission and the end of transmission. This SoT / EoT detection can be done by observing the input signal in a large enough window to make a robust decision. For example, a change from a low signal level to a high signal level triggers a SoT event, while a change from a high signal level to a low signal level and remaining low for a certain period of time triggers an EoT event.

[0067] When the SoT trigger signal is received, the switch controller 240 issues a control signal to the power switch 220 to start delivering power to the pulse amplifier 260 and the LED module 210. When the EoT trigger signal is received, the switch controller 240 arranges for the shutdown command to occur after a sufficiently long waiting interval to allow all delayed TX signals to be transmitted via the LED 210. The switch controller 240 can optionally use a timer that will keep the switch active for the longest possible data packet size and avoid EoT detection. However, since the actual packet length may vary and is typically less than the longest possible data packet size, a fixed on interval will be less effective in saving energy than EoT-based switch control.

[0068] The signal interface unit (SI) 250 can be implemented as a delay unit, for example, using an all-pass filter that introduces a predefined amount of delay to all subcarriers in the OFDM signal. Since the pulse amplifier 260 and the LED 210 have a fast response, the required amount of delay is quite small, which means that a few components are usually sufficient to implement the delay. Another option that does not require a delay unit is to keep the amplifier input at zero level for a short duration after the SoT detection arrives, so that the LED output light level stabilizes at an average (DC) level and is then connected to the incoming TX signal for modulating the LED light level. This option can be implemented as an analog signal multiplexer.

[0069] The above scheme can be alternatively implemented by explicitly providing a dedicated transmission start signal before the normal packet preamble to enable power control of the OFE. This physical layer extension will allow power switch control without the need for signal delays, as the OFEs will enter their ready state before the start of the normal packet. Figure 4 An example of such a packet structure of an input signal is illustrated. Additional fields are added to the normal data packet. When we are talking about a standards compliant system, this option represents a PHY layer extension of the data frame, such as according to G.VLC (G.9991), with an additional preamble interval for standby control. During this interval, a predefined signal is sent to the OFE to generate a SoT trigger. The data in the additional field, or so called standby control segment, may simply be an extension of the original preamble signal of the data frame, which was originally used for synchronization purposes. Such an extension may possibly be implemented as a firmware update in current chipsets to increase the length of the preamble.

[0070] Figure 5 A block diagram of a system 400 for optical wireless communication is shown. As a basic setup, the system 400 includes an optical front end 201 and a modem 300. The optical front end 201 includes a light source 210, a power switch 220, a detector 230, and a switch controller 240. The light source 210 is configured to emit light for optical wireless communication based on an input signal to be transmitted via the optical front end 201. The power switch 220 is configured to turn on or off power to the light source 210. The detector 230 is configured to detect an input signal on a signal path of the optical front end 201; and send a trigger signal related to the start of transmission SoT of the input signal to the switch controller 240. The switch controller 240 is configured to control the power switch 220 to power on the light source 210 upon receiving a first trigger signal. The modem 300 is configured to extend the packet to be transmitted by adding an additional field at the beginning of the packet, such as Figure 3The duration of the additional field is determined according to the stabilization time of the light source 210 of the optical front end 201, and the extended packet is sent to the optical front end 201 as an input signal.

[0071] Figure 6 A flow chart of a method 600 of an optical transmitter 100 is shown. The method 600 includes the following steps of the optical transmitter 100: in step S601, based on an input signal including a data signal to be transmitted via the optical transmitter 100, light for optical wireless communication is emitted through the light source 210; in step S602, power to the light source 210 is turned on or off through the power switch 220; in step S603, an input signal on a signal path of the optical transmitter 100 is detected; in step S604, a first trigger signal related to a start of transmission SoT of the input signal is sent to the switch controller 240; in step S605, the power switch 220 is controlled to power on the light source 210 upon receiving the first trigger signal; in step S606, data signals are prevented from being transmitted during a first time interval after the light source 210 is powered on; and in step S607, data signals are transmitted during a second time interval subsequent to the first time interval. The first time interval is determined based on a stabilization time of the light source 210.

[0072] The method according to the present invention can be implemented on a computer as a computer-implemented method, or in dedicated hardware, or in a combination of both.

[0073] The executable code of the method according to the invention may be stored on a computer / machine readable storage device. Examples of computer / machine readable storage devices include non-volatile memory devices, optical storage media / devices, solid-state media, integrated circuits, servers, etc. Preferably, the computer program product comprises non-transitory program code means stored on a computer readable medium for performing the method according to the invention when the program product is executed on a computer.

[0074] Methods, systems, and computer-readable media (transitory and non-transitory) may also be provided to implement selected aspects of the above-described embodiments.

Claims

1. An optical transmitter (100) configured to transmit a data signal for optical wireless communication, the optical transmitter (100) comprising: - a light source (210) configured to emit light for optical wireless communication based on an input signal including a data signal to be transmitted via the optical transmitter (100); - a power switch (220) configured to turn on or off power to the light source (210); - a detector (230) configured to: - detecting an input signal on a signal path of said optical transmitter (100); and - sending a first trigger signal associated with the start of transmission SoT of the input signal to a switch controller (240); - a switch controller (240), configured to control the power switch (220) to power on the light source (210) when receiving the first trigger signal; The optical transmitter (100) is configured as follows: - preventing the transmission of data signals during a first time interval after the light source (210) is powered on; and - transmitting said data signal during a second time interval subsequent to said first time interval; The first time interval is determined based on a stabilization time of the light source (210).

2. The optical transmitter (100) of claim 1, wherein the detector (230) is configured to observe an average signal strength of an input signal on the signal path within a time window and detect the SoT when the average signal strength is above a predefined threshold.

3. The optical transmitter (100) according to claim 1 or 2, wherein the detector (230) is further configured to - detect an end of transmission EoT of an input signal on the signal path; and - sending a second trigger signal related to EoT to the switch controller (240); and the switch controller (240) is configured to control the power switch (220) to turn off the power to the light source (210) after a certain delay when receiving the second trigger signal, and the certain delay is at least equal to the propagation delay of the input signal from the detector (230) to the light source (210).

4. The optical transmitter (100) according to claim 1 or 2, wherein the switch controller (240) is configured to control the power switch (220) to power off the light source (210) after a predefined maximum packet duration when receiving a first trigger signal.

5. The optical transmitter (100) according to any one of the preceding claims, wherein the power switch (220) is placed at the output of a driver of the light source (210).

6. An optical transmitter (100) according to any of the preceding claims, wherein the optical transmitter (100) is configured to extend the packet to be transmitted by adding an additional field at the beginning of the packet; wherein the duration of the additional field is determined according to the first time interval, and the extended packet is sent to the light source (210) as an input signal.

7. An optical transmitter (100) according to any one of the preceding claims 1-5, wherein the optical transmitter (100) further comprises a signal interface (250), wherein the signal interface (250) is configured to add an additional delay in a signal path of the optical transmitter (100) before the light source (210); wherein the additional delay is determined based on the first time interval.

8. The optical transmitter (100) according to claim 7, further comprising an amplifier connected between the signal interface (250) and the light source (210).

9. The optical transmitter (100) according to claim 7 or 8, wherein the signal interface (250) is a delay unit.

10. The optical transmitter (100) of claim 7 or 8, wherein the signal interface (250) is an analog signal multiplexer.

11. The optical transmitter (100) according to any of the preceding claims, wherein the data signal is modulated according to intensity modulation.

12. An optical front end (200) configured to transmit a data signal for optical wireless communication, the optical front end (200) comprising: - a light source (210) configured to emit light for optical wireless communication based on an input signal including a data signal to be transmitted via the optical front end (200); - a power switch (220) configured to turn on or off power to the light source (210); - a detector (230) configured to: - detecting an input signal on a signal path of the optical front end (200); and - sending a first trigger signal associated with the start of transmission SoT of the input signal to the switch controller (240); - a switch controller (240), configured to control the power switch (220) to power on the light source (210) upon receiving the first trigger signal; and - a signal interface (250) configured to add an additional delay in the signal path before the light source (210); wherein the additional delay is determined according to a settling time of the light source (210).

13. A method (600) for reducing standby power consumption in an optical transmitter (100), wherein the optical transmitter (100) is configured to transmit data signals for optical wireless communication; the method comprising the steps of: - emitting light (S601) for optical wireless communication by means of a light source (210) based on an input signal including a data signal to be transmitted via an optical transmitter (100); - turning on or off (S602) the power to the light source (210) via the power switch (220); - detecting (S603) an input signal on a signal path of the optical transmitter (100); - sending (S604) a first trigger signal associated with the start of transmission SoT of the input signal to the switch controller (240); - upon receiving the first trigger signal, controlling (S605) the power switch (220) to power on the light source (210); - preventing (S606) transmission of data signals during a first time interval after the light source (210) is powered on; and - transmitting (S607) the data signal during a second time interval subsequent to the first time interval; The first time interval is determined based on a stabilization time of the light source (210).

14. The method according to claim 13, further comprising: - Detecting the end of transmission EoT of the input signal on the signal path; - sending a second trigger signal related to EoT to the switch controller (240); - upon receiving the second trigger signal, controlling the power switch (220) to de-energize the light source (210) after a certain delay, and the certain delay is at least equal to the propagation delay of the data signal from the detector (230) to the light source (210).

15. The method according to claim 13, further comprising: - upon receiving the first trigger signal, controlling the power switch (220) to de-energize the light source (210) after a predefined maximum packet duration.

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