An underwater differential optical communication device and method

Abstract

The present invention discloses a method for differential optical communication applicable to underwater, including step S1: The PWM modulator digitally encodes the signal level emitted by the signal source and drives the cold and warm LEDs to send corresponding signals according to the duty cycle of the dual light sources. Step S2: The dual light sources emitted by the cold and warm LEDs are adjusted into parallel light beams under the action of a lens. Step S3: The dual light sources passing through the waterway pass through a filter to filter out interfering light, and then pass through a lens to focus the diverging light beam into a photodetector. Step S4: The electrical signal converted by the photodetector enters an amplifier for amplification processing. Step S4: The amplified electrical signal enters a PWM demodulator to be restored to a modulation signal. This method can be applied to the field of underwater optical communication. There is no need to measure the absolute value of the received light intensity, only the color of the received light needs to be measured, and attention is paid to the relative ratio of the light intensities of the dual light sources, solving the problem of large attenuation of LED light underwater, extending the communication distance, and reducing the bit error rate.

Description

Technical Field

[0001] The present invention belongs to the field of underwater optical communication, and particularly relates to a differential optical communication device and method suitable for underwater use. Background Art

[0002] With the continuous in-depth development of ocean exploration technology, people have put forward higher requirements for high-speed and long-distance underwater wireless communication technology. In recent years, with the continuous increase in the demand for underwater communication rate, traditional wireless communication technologies such as electromagnetic waves and sound waves can no longer meet the needs of ocean communication. The application of space optical communication technology in the field of underwater communication is becoming more and more extensive. Underwater wireless optical communication has become a research hotspot in current underwater communication due to its advantages such as high transmission rate, large capacity, low power consumption, and small volume.

[0003] However, seawater is a complex physical, chemical, and biological combination system, which contains dissolved substances, suspended solids, and many various active organisms. Due to the inhomogeneity of substances and suspended solids in seawater, light waves are attenuated due to absorption and scattering during underwater propagation. The underwater transmission characteristics of light waves are one of the important factors restricting the quality of underwater optical wireless communication, and it has an important impact on the determination of the design scheme of the entire underwater optical wireless communication system.

[0004] Based on this, the present application proposes a method for differential optical communication suitable for underwater use to solve the above problems, extend the communication distance, and reduce the bit error rate. Summary of the Invention

[0005] The object of the present invention is to overcome the deficiencies in the prior art and provide a method for differential optical communication suitable for underwater use, which can be applied to the field of underwater optical communication. It is not necessary to measure the absolute value of the received light intensity, but only to measure the color of the received light. The focus is on the light intensity ratio between composite light sources, solving the problem of large attenuation of LED light underwater, extending the communication distance, and reducing the bit error rate.

[0006] The object of the present invention is to provide a method for differential optical communication suitable for underwater use.

[0007] Preferably, the method is to encode and decode a composite light source composed of two basic light sources of two colors.

[0008] Preferably, the two basic light sources of the two colors are white LEDs, one is a cold light source, and the other is a warm light source.

[0009] Preferably, the color temperature range of the cold basic light source is above 5000K; the color temperature range of the warm basic light source is below 4000K.

[0010] Preferably, the PWM signal is a constant current square wave signal with a frequency not less than 50 Hz.

[0011] Preferably, the two basic light sources can be described by duty cycle, luminous measure, color coordinates, and light color ratio.

[0012] Preferably, the basic luminous measure or the mixed light luminous measure is any one of the physical quantities of luminous flux, luminous intensity, luminance, or illuminance.

[0013] Preferably, the mixed light source is transmitted after being encoded at the transmitting end and decoded after being received at the receiving end.

[0014] Preferably, the encoding formula at the transmitting end is:

[0015]

[0016] where: x m , y m represent the color coordinates of the mixed light source; x c , y c and x w , y w are respectively the color coordinates of the cold basic light source and the warm basic light source participating in the mixed light at a duty cycle of 100%, D c and D w are respectively the duty cycles of the cold and warm basic light sources, L c and L w are respectively the luminous measures of the cold basic light source and the warm basic light source participating in the mixed light at a duty cycle of 100%, R c = L c / y c , R w = L w / y w respectively represent the light color ratios of the cold and warm basic light sources.

[0017] Preferably, the decoding formula at the receiving end is:

[0018]

[0019] where: x m , y m represent the color coordinates of the mixed light source; x c , y c and x w , y w are respectively the color coordinates of the cold basic light source and the warm basic light source participating in the mixed light at a duty cycle of 100%, D c and D w are respectively the duty cycles of the cold and warm basic light sources, L c and L w are respectively the luminous measures of the cold basic light source and the warm basic light source participating in the mixed light at a duty cycle of 100%, Rc = L c / y c 、R w = L w / y w respectively represent the light color ratios of the cold and warm basic light sources.

[0020] Preferably, the processes of the encoding method and the decoding method are inverse to each other.

[0021] The present invention also provides an apparatus for implementing the method for underwater differential optical communication as described above, including a transmitting end and a receiving end. The transmitting end emits a light source, and the receiving end receives the light source emitted by the transmitting end. The light source is a composite light source composed of two-color basic light sources. The transmitting end includes a signal source, a PWM modulator, and a cold-warm LED that are sequentially signal-connected. A lens one is provided at the emitting end of the cold-warm LED. The receiving end includes a photodetector and a PWM demodulator that are sequentially signal-connected. A filter and a lens two are sequentially provided at the light receiving end of the photodetector from outside to inside. An amplifier is connected between the photodetector and the PWM modulator.

[0022] Advantages of the present invention: In the field of underwater optical communication, according to the differential method, instead of measuring the absolute magnitudes of the intensities of two beams of light, the ratio of the duty cycles of the two beams of light is measured. Although there is noise, as long as the attenuation is similar, the ratio is almost the same, which can improve the communication system. Brief Description of the Drawings

[0023] Figure 1 is a schematic diagram of the apparatus according to an embodiment of the present invention;

[0024] Figure 2 is a differential schematic diagram in an embodiment of the present invention;

[0025] Figure 3 is a schematic diagram of an embodiment of the encoding and decoding methods of the present invention. Detailed Embodiments

[0026] To facilitate the understanding of the present invention, the present invention will be described in more detail below with reference to the drawings and specific embodiments. Preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0027] It should be noted that, unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0028] This embodiment provides a method for underwater differential optical communication, and the method includes:

[0029] Step S1: The PWM modulator digitally encodes the signal level emitted by the signal source and drives the warm and cold LEDs by sending corresponding signals according to the duty cycles of the two light sources.

[0030] Step S2: The two light sources emitted by the warm and cold LEDs are adjusted into parallel light beams under the action of the lens.

[0031] Step S3: The two light sources passing through the water path pass through the filter to filter out the interfering light, and then pass through the lens to focus the divergent light beam on the photodetector.

[0032] Step S4: The electrical signal converted by the photodetector enters the amplifier for amplification processing.

[0033] Step S4: The amplified electrical signal enters the PWM demodulator and is restored to the modulation signal.

[0034] The core parameter is the duty cycle D of the two basic light sources, which represents the ratio of the time when the square wave pulse signal is in the "on" state to the entire square wave period.

[0035] The warm and cold LEDs include a white warm light source capable of emitting a color temperature less than 4000K and a white cold light source with a color temperature greater than 5000K.

[0036] Wherein, the photometric quantity is any one of the physical quantities such as luminous flux, luminous intensity, luminance or illuminance.

[0037] For square wave pulse signals with different duty cycles, the basic photometric quantities of the basic light sources are different. Taking the photometric quantity of the basic light source when the duty cycle is 100% as the basic photometric quantity, the basic photometric quantity is denoted as L i .

[0038] In this embodiment, the encoding and decoding methods are as Figure 3 shown. The described encoding method and the color decoding method, the encoding method and the decoding method process are inverse to each other.

[0039] Specifically, the encoding formula is:

[0040]

[0041] Where: x m , y m represent the chromaticity coordinates of the mixed light source; x c , y c and x w , y w are respectively the chromaticity coordinates of the cold light source and the warm light source participating in the mixed light at a duty cycle of 100%, D c and D w are respectively the duty cycles of the cold and warm light sources, L c and L w are respectively the luminous fluxes of the cold light source and the warm light source participating in the mixed light at a duty cycle of 100%, R c = L c / y c , R w = L w / y w respectively represent the light color ratios of the cold and warm light sources.

[0042] Specifically, the decoding and encoding formula is:

[0043]

[0044] Where: x m , y m represent the chromaticity coordinates of the mixed light source; x c , y c and x w , y w are respectively the chromaticity coordinates of the cold light source and the warm light source participating in the mixed light at a duty cycle of 100%, D c and D w are respectively the duty cycles of the cold and warm light sources, L c and L w are respectively the luminous fluxes of the cold light source and the warm light source participating in the mixed light at a duty cycle of 100%, R c = L c / y c , R w = L w / y w respectively represent the light color ratios of the cold and warm light sources.

[0045] Figure 2 Shows the differential method of the present invention, the method comprising: two square wave signals.

[0046] The core parameter is the duty cycle D, which represents the ratio of the time when the square wave pulse signal is in the "on" state to the entire square wave period.

[0047] Furthermore, the duty cycle is:

[0048]

[0049] Where: t1 and t2 are the "on" state times of the two square wave signals respectively, T1 and T2 are the periods of the two square waves respectively, and D1 and D2 are the duty cycles of the two square waves respectively.

[0050] Furthermore, the duty cycle ratio is:

[0051]

[0052] Where: D1 and D2 are the duty cycles of the two square waves respectively, is the ratio of the duty cycles of the two square waves.

[0053] Specifically, the color difference method is that in the field of underwater optical communication, instead of measuring the intensities of the two light sources, the ratio of the duty cycles of the two light sources is measured. Although there is noise, as long as the attenuation is similar, their ratio is almost the same.

[0054] This embodiment also provides a differential optical communication device applicable to underwater, as Figure 1 shown, including a transmitting end and a receiving end. The transmitting end emits a light source, and the receiving end receives the light source emitted by the transmitting end. The light source is a composite light source composed of two basic light sources of different colors.

[0055] The transmitting end includes a signal source, a PWM modulator, and a cold and warm LED that are sequentially signal-connected.

[0056] Among them, the PWM modulator digitally encodes the analog signal level emitted by the signal source and sends a corresponding signal to drive the cold and warm LED according to the ratio of the duty cycles of the two light sources.

[0057] Furthermore, a lens 1 is provided at the transmitting end of the cold and warm LED. Under the action of the lens 1, the composite light source adjusts the light beam into a parallel light beam.

[0058] Furthermore, the receiving end includes a photodetector and a PWM demodulator that are sequentially signal-connected. Among them, the light receiving end of the photodetector is sequentially provided with a filter and a lens 2 from the outside to the inside.

[0059] The filter is used to filter out interfering light, and then through the lens 2, the diverging light beam is focused on the photodetector as much as possible. Among them, the electrical signal converted by the photodetector enters an amplifier for amplification processing. And the amplified electrical signal enters the PWM demodulator to be restored to a modulated signal.

[0060] The above examples are only preferred examples of the present invention and are not intended to limit the present invention. For those skilled in the art, various modifications and variations can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for underwater differential optical communication, characterized in that, It includes the following steps: S1. Form a composite light source composed of two-color basic light sources; S2. Encode the composite light source at the transmitting end; S3. Transmit after encoding at the transmitting end and decode after receiving at the receiving end; In the step S2, the encoding method has the following expression: where: x m , y m represent the chromaticity coordinates of the mixed light source; x c , y c and x w , y w are the chromaticity coordinates of the cold basic light source and the warm basic light source participating in the light mixing under a duty cycle of 100%, D c and D w are the duty cycles of the cold and warm basic light sources respectively, L c and L w are the luminous fluxes of the cold basic light source and the warm basic light source participating in the light mixing under a duty cycle of 100% respectively, R c = L c / y c , R w = L w / y w represent the luminous color ratios of the cold and warm basic light sources respectively; In the step S3, the decoding method has the following expression: Where: x m , y m represent the chromaticity coordinates of the mixed light source; x c , y c and x w , y w are respectively the chromaticity coordinates of the cold basic light source and the warm basic light source participating in the light mixing under a duty cycle of 100%, D c and D w are respectively the duty cycles of the cold and warm basic light sources, L c and L w are respectively the luminous fluxes of the cold basic light source and the warm basic light source participating in the light mixing under a duty cycle of 100%, R c = L c / y c , R w = L w / y w respectively represent the luminous color ratios of the cold and warm basic light sources.

2. The method for underwater differential optical communication according to claim 1, wherein The two-color basic light sources are white LEDs, one is a cold light source and the other is a warm light source.

3. The method for underwater differential optical communication according to claim 2, wherein The color temperature range of the cold basic light source is above 5000K.

4. A method for underwater differential optical communication according to claim 2, characterized in that, The color temperature range of the warm basic light source is below 4000K.

5. A method for underwater differential optical communication according to claim 1, characterized in that, The luminous quantity of the composite light source is any one of the physical quantities of luminous flux, luminous intensity, luminance, and illuminance.

6. An apparatus for implementing the method of underwater differential optical communication according to any one of claims 1-5, characterized in that, It includes a transmitting end and a receiving end. The transmitting end emits a light source, and the receiving end receives the light source emitted by the transmitting end. The light source is a composite light source composed of two-color basic light sources.

7. The device according to claim 6, characterized in that, The transmitting end includes a signal source, a PWM modulator, and a cold-warm LED that are sequentially signal-connected.

8. The device according to claim 7, characterized in that, A lens 1 is provided at the emitting end of the cold-warm LED.

9. The device according to claim 6, characterized in that, The receiving end includes a photodetector and a PWM demodulator that are sequentially signal-connected.

10. The device according to claim 9, characterized in that, A filter and a lens 2 are sequentially provided from the outside to the inside at the light receiving end of the photodetector. An amplifier is connected between the photodetector and the PWM modulator.

Images