Multi-channel optical transmission device based on periodic optical filter

Abstract

The invention discloses a multichannel optical transmission device based on periodic optical filters. The multichannel optical transmission device comprises a multichannel light source, a phase modulator array, a multi-wavelength light beam combiner, a light beam splitter, a first periodic optical filter, a second periodic optical filter and a balanced photoelectric detector. Multi-channel radio frequency signals are modulated to optical signals with different frequencies through the phase modulator array, bias point closed-loop control is not needed, the modulated optical signals are transmitted through the same optical fiber, the number of transmission optical fibers can be reduced, phase differences and intermodulation in the transmission process of the multi-channel radio frequency signals can be reduced, and the transmission efficiency of the multi-channel radio frequency signals can be improved. An upper sideband and a lower sideband of a radio-over-fiber signal are respectively filtered out through the periodic band-pass filter, demodulation of a phase modulation signal is realized through an upper sideband signal and a lower sideband signal through the balance detector, optical transmission common-mode noise and even-order harmonics are reduced, the optical transmission signal-to-noise ratio and the harmonic suppression ratio can be improved, the integration level is high, use is flexible, and the application range is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of optical transmission, and in particular to a multi-channel optical transmission device based on a periodic optical filter. Background Art

[0002] RF optical transmission has a wide range of applications due to its broadband, low loss, and anti-electromagnetic interference performance. In most scenarios, multi-channel RF signals need to be transmitted simultaneously, and the simultaneous transmission of multi-channel RF signals needs to have low noise, low spectral intermodulation, and high harmonic suppression performance. Currently, single-channel optical transmission can reduce common-mode noise and improve the harmonic suppression ratio by combining phase modulation with balanced detection. However, for multi-channel RF optical transmission needs, each RF channel corresponds to a set of transmission modules. Simple stacking and expansion of optical transmission devices will make the entire optical transmission link complicated, and the inconsistency of the optical paths of each optical transmission device will lead to large differences in the phase of multi-channel RF signal transmission. By directly modulating multi-channel RF signals onto the same optical signal, there will be problems such as large intermodulation between multi-channel RF signals.

[0003] Therefore, it is particularly important to propose a device suitable for low-noise, low-spectral intermodulation, and high-harmonic suppression optical transmission of multi-channel radio frequency signals. Summary of the invention

[0004] In order to solve the technical problems existing in the background technology, the present invention proposes a multi-channel optical transmission device based on a periodic optical filter.

[0005] The multi-channel optical transmission device based on a periodic optical filter proposed by the present invention comprises:

[0006] A multi-channel light source, located at the transmitting end of the multi-channel optical transmission device, for outputting a plurality of optical signals of different wavelengths;

[0007] A phase modulator array, located at the transmitting end of the multi-channel optical transmission device, is used to receive a multi-channel radio frequency input signal and complete the electro-optical conversion of the multi-channel radio frequency input signal to obtain a multi-channel optical signal after the electro-optical conversion;

[0008] A multi-wavelength optical combiner, located at the transmitting end of the multi-channel optical transmission device, for combining the multi-channel optical signals after optical conversion to obtain a first combined signal;

[0009] an optical beam splitter, located at a receiving end of the multi-channel optical transmission device, for receiving the first combined beam signal and performing beam splitting processing on the first combined beam signal to obtain a first optical signal and a second optical signal;

[0010] A first periodic optical filter, located at a receiving end of the multi-channel optical transmission device, is used to filter out an optical carrier and an upper sideband signal from the first optical signal to obtain a first output optical signal;

[0011] A second periodic optical filter, located at a receiving end of the multi-channel optical transmission device, is used to filter out an optical carrier and a lower sideband signal from the second optical signal to obtain a second output optical signal;

[0012] The balanced photodetector is located at the receiving end of the multi-channel optical transmission device, and is used to receive the first output optical signal and the second output optical signal, and complete the photoelectric conversion and balanced reception of the first output optical signal and the second output optical signal to obtain a multi-channel radio frequency signal.

[0013] Preferably, the multi-channel light source has n output channels, each channel outputs an optical signal, and the wavelengths of the optical signals corresponding to the n output channels are different, and the difference in optical frequency between adjacent channels among the n output channels is a fixed value Δυ.

[0014] Preferably, the multi-channel light source is specifically a plurality of lasers with different wavelengths.

[0015] Preferably, the multi-channel light source is composed of a single-frequency laser cascaded optical microring and an arrayed waveguide grating.

[0016] Preferably, the phase modulator array includes n phase modulators, and the n phase modulators correspond one-to-one to the n output channels of the multi-channel light source.

[0017] Preferably, the multi-wavelength optical beam combiner is an arrayed waveguide grating.

[0018] Preferably, the multi-wavelength optical combiner is a wavelength division multiplexer.

[0019] Preferably, the first periodic optical filter is specifically a periodic bandpass filter, the adjacent passband frequency interval of the first periodic optical filter is Δυ, and the first periodic optical filter passes the optical carrier and the upper sideband signal of the input first optical signal and blocks the lower sideband signal.

[0020] Preferably, the second periodic optical filter is specifically a periodic bandpass filter, the adjacent passband frequency interval of the second periodic optical filter is Δυ, and the second periodic optical filter passes the optical carrier and the lower sideband signal of the input second optical signal, and blocks the upper sideband signal.

[0021] In the present invention, the proposed multi-channel optical transmission device based on periodic optical filter, the multi-channel light source outputs a plurality of optical signals of different wavelengths, each wavelength optical signal is respectively passed through each phase modulator in the phase modulator array to complete the electro-optical conversion of the multi-channel radio frequency input signal, the optical signal after electro-optical conversion is combined by the multi-wavelength optical combiner, the combined optical signal is transmitted to the optical beam splitter through the optical fiber and is divided into two beams of light, one of which is filtered out by the first periodic optical filter to filter out the optical carrier and the upper sideband signal, and the other optical signal is filtered out by the second periodic optical filter to filter out the optical carrier and the lower sideband signal, the first periodic optical filter and the second periodic optical filter output optical signals are input into the balanced photodetector to complete the photoelectric conversion and balanced reception, and the multi-channel radio frequency signal transmitted by the device is output. By modulating the multi-channel radio frequency signals to optical signals of different frequencies respectively, the modulated optical signals are transmitted through the same optical fiber, on the one hand, the number of transmission optical fibers is reduced, and on the other hand, the transmission paths of the multi-channel radio frequency signals are consistent, which can reduce the phase difference between the multi-channel radio frequency signals during the transmission process, and the frequency difference of the optical signals of different frequencies is much greater than the frequency of the radio frequency signal, which can reduce the radio frequency signal intermodulation generated by the transmission of the multi-channel radio frequency signals on the same optical fiber. The upper and lower sidebands of the optical radio frequency signal are filtered out by a periodic bandpass filter respectively. The upper and lower sideband signals are demodulated by a balanced detector to realize phase modulation signal demodulation. The balanced detector reduces the common mode noise and even harmonics of optical transmission, which can improve the signal-to-noise ratio and harmonic suppression ratio of optical transmission. Multiple optical radio frequency signals are filtered and processed simultaneously by a periodic bandpass filter, and the phase modulation and demodulation of the radio frequency signals of all channels are completed by a balanced detector, which greatly reduces the number of balanced detectors and filters required for multi-channel optical transmission. The optical beam splitter, the first periodic optical filter, the second periodic optical filter and the balanced photodetector required by the receiving end can all be prepared by integrated chips, with high integration. At the same time, the phase modulator does not require bias point closed-loop control compared to the intensity modulator, and the modulation system is simple, small in size and low in power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the architecture of a multi-channel optical transmission device based on a periodic optical filter proposed by the present invention;

[0023] Figure 2 This is a structural schematic diagram of a transmitting end embodiment 1 of a multi-channel optical transmission device based on a periodic optical filter proposed by the present invention;

[0024] Figure 3 This is a structural schematic diagram of a transmitting end embodiment 2 of a multi-channel optical transmission device based on a periodic optical filter proposed by the present invention;

[0025] Figure 4 This is a structural schematic diagram of a receiving end embodiment 1 of a multi-channel optical transmission device based on a periodic optical filter proposed by the present invention;

[0026] Figure 5 This is a spectrum diagram of a first periodic optical filter of a multi-channel optical transmission device based on a periodic optical filter proposed by the present invention;

[0027] Figure 6 This is a spectrum diagram of the second periodic optical filter of the multi-channel optical transmission device based on periodic optical filters proposed by the present invention. DETAILED DESCRIPTION

[0028] Reference Figure 1-6 The multi-channel optical transmission device based on the periodic optical filter proposed by the present invention comprises:

[0029] The multi-channel light source 1 is located at the transmitting end of the multi-channel light transmission device and is used to output a plurality of light signals with different wavelengths.

[0030] In this embodiment, the multi-channel light source 1 has n output channels, each channel outputs an optical signal, and the wavelengths of the optical signals corresponding to the n output channels are different, and the difference in optical frequency between adjacent channels in the n output channels is a fixed value Δυ. Each channel outputs optical signals of different frequencies, and the optical frequencies are υ1, ..., υ n , fixed value Δυ, that is, υ m -υ m-1 =Δυ; where 2≤m≤n.

[0031] The phase modulator array 2 is located at the transmitting end of the multi-channel optical transmission device, and is used to receive the multi-channel RF input signal and complete the electro-optical conversion of the multi-channel RF input signal to obtain the multi-channel optical signal after the electro-optical conversion.

[0032] In this embodiment, the phase modulator array 2 includes n phase modulators, and the n phase modulators correspond one to one to the n output channels of the multi-channel light source 1. The phase modulator array 2 includes n phase modulators, and for the input n channel RF signals, the RF signal frequencies are f1, ..., f n , the mth phase modulator converts the mth RF signal (frequency f n ) modulated to the mth channel optical signal (frequency is υ m ) to complete the electro-optical conversion, where 2≤m≤n.

[0033] The multi-wavelength optical combiner 3 is located at the transmitting end of the multi-channel optical transmission device and is used to combine the multi-channel optical signals after optical conversion to obtain a first combined signal.

[0034] The optical beam splitter 4 is located at the receiving end of the multi-channel optical transmission device, and is used to receive the first combined beam signal and perform beam splitting processing on the first combined beam signal to obtain a first optical signal and a second optical signal.

[0035] The first periodic optical filter 5 is located at the receiving end of the multi-channel optical transmission device and is used to filter out the optical carrier and the upper sideband signal of the first optical signal to obtain a first output optical signal.

[0036] In this embodiment, the first periodic optical filter 5 is specifically a periodic bandpass filter. The adjacent passband frequency interval of the first periodic optical filter 5 is Δυ. The first periodic optical filter 5 passes the optical carrier and the upper sideband signal of the input first optical signal and blocks the lower sideband signal.

[0037] The second periodic optical filter 6 is located at the receiving end of the multi-channel optical transmission device and is used to filter out the optical carrier and the lower sideband signal of the second optical signal to obtain a second output optical signal.

[0038] In this embodiment, the second periodic optical filter 6 is specifically a periodic bandpass filter. The adjacent passband frequency interval of the second periodic optical filter 6 is Δυ. The second periodic optical filter 6 passes the optical carrier and the lower sideband signal of the input second optical signal, and blocks the upper sideband signal.

[0039] The balanced photodetector 7 is located at the receiving end of the multi-channel optical transmission device, and is used to receive the first output optical signal and the second output optical signal, and complete the photoelectric conversion and balanced reception of the first output optical signal and the second output optical signal to obtain a multi-channel radio frequency signal.

[0040] Specifically, Figure 1 As shown, a multi-channel light source 1, a phase modulator array 2 and a multi-wavelength optical combiner 3 constitute a transmitting end, and an optical beam splitter 4, a first periodic optical filter 5, a second periodic optical filter 6 and a balanced photodetector (7) constitute a receiving end. The transmitting end completes the electro-optical conversion of the multi-channel radio frequency signal and transmits it to the receiving end via the optical fiber. The receiving end completes the photoelectric conversion of the optically carried radio frequency signal and outputs the multi-channel radio frequency signal. The connection relationship of each device in the device is as follows:

[0041] The multi-channel light source 1 outputs a plurality of optical signals of different wavelengths, and the optical signals of each wavelength are respectively passed through each phase modulator in the phase modulator array 2 to complete the electro-optical conversion of the multi-channel radio frequency input signal. The optical signals after electro-optical conversion are combined by the multi-wavelength optical combiner 3, and the combined optical signals are transmitted to the optical beam splitter 4 through the optical fiber and divided into two beams of light, wherein one optical signal passes through the first periodic optical filter 5 to filter out the optical carrier and the upper sideband signal, and the other optical signal passes through the second periodic optical filter 6 to filter out the optical carrier and the lower sideband signal. The optical signals output by the first periodic optical filter 5 and the second periodic optical filter 6 are input into the balanced photodetector 7 to complete the photoelectric conversion and balanced reception, and the multi-channel radio frequency signal transmitted by the device is output.

[0042] Embodiment 1 of the transmitting end is as follows:

[0043] like Figure 2As shown, the multi-channel light source 1 is specifically a plurality of lasers with different wavelengths. The multi-channel light source 1 is composed of n lasers with different wavelengths, and the frequency of the output optical signal of the laser m is v m , the mth phase modulator converts the mth RF signal (frequency f m ) modulated to the laser m optical signal (frequency is υ m ) to complete the electro-optical conversion, where 2≤m≤n. The multi-wavelength optical combiner 3 is a wavelength division multiplexer, and the optical signals output by the n phase modulators are combined by the wavelength division multiplexer and transmitted through the same optical fiber. In this embodiment, the n lasers, n phase modulators and wavelength division multiplexers all have corresponding discrete device solutions, and this embodiment can be implemented by cascading discrete devices.

[0044] Embodiment 2 of the transmitting end is as follows:

[0045] like Figure 3 As shown, the multi-channel light source 1 is composed of a single-frequency laser 11 cascaded optical microring 12 and a first arrayed waveguide grating 13. The single-frequency laser outputs an optical signal with a frequency of υ0, and the optical signal passes through the optical microring to output n frequencies of υ1, ..., υ n The first arrayed waveguide grating 13 performs spectrum separation on the optical frequency comb signal to separate it into n channels, and the frequencies are υ1, ..., υ n The n phase modulators respectively modulate the n RF input signals into n single-frequency optical signals to complete the electro-optical conversion. The multi-wavelength optical combiner 3 is a second arrayed waveguide grating, and the n phase modulator output optical signals are combined through the second arrayed waveguide grating and transmitted through the same optical fiber. In this embodiment, the single-frequency laser 11, the optical microring 12, the first arrayed waveguide grating 13, the phase modulator array 2 and the second arrayed waveguide grating can all be prepared by chip tape-out, and the present embodiment can be implemented by single-chip or multi-chip integration.

[0046] The receiving end receives the optical signal sent by the transmitting end, completes the photoelectric conversion of the optically carried radio frequency signal, and outputs a multi-channel radio frequency signal. Figure 4 As shown, the receiving end divides the optical signal sent by the transmitting end into two beams of light through the optical beam splitter 4, and the first periodic optical filter 5 and the second periodic optical filter 6 complete the upper and lower sideband separation of the optical radio frequency signal sent by the transmitting end, and the photoelectric conversion and balanced detection of the upper and lower sidebands of the optical radio frequency signal are realized in combination with the balanced photodetector 7. The first periodic optical filter 5 and the second periodic optical filter 6 are periodic bandpass filters, which can be realized by cascading optical microrings.

[0047] The adjacent passband frequency interval of the first periodic optical filter 5 is Δυ. For the input optical carrier (frequency is υ m ), upper sideband (frequency is υ m +Nfm ) and the lower sideband (frequency is υ m -Nf m ) signal, the first periodic optical filter 5 passes the optical carrier and the upper sideband signal, and blocks the lower sideband signal, wherein N is the order of the electro-optical conversion harmonics, N≥1, 2≤m≤n. The spectrum of the first periodic optical filter 5 and the spectrum of the optical signal input to the filter are as follows: Figure 5 As shown. The adjacent passband frequency interval of the second periodic optical filter 6 is Δυ. For the input optical carrier (frequency is υ m ), upper sideband (frequency is υ m +Nf m ) and the lower sideband (frequency is υ m -Nf m ) signal, the second periodic optical filter 6 passes the optical carrier and the lower sideband signal, and blocks the upper sideband signal, wherein N is the order of the electro-optical conversion harmonics, N≥1, 2≤m≤n. The spectrum of the second periodic optical filter 6 and the spectrum of the optical signal input to the filter are as follows: Figure 6 In this embodiment, the optical beam splitter 4, the first periodic optical filter 5, the second periodic optical filter 6 and the balanced photodetector 7 can all be prepared by chip tape-out, and this embodiment can be implemented by single-chip or multi-chip integration.

[0048] In the specific working process of the multi-channel optical transmission device based on the periodic optical filter of this embodiment, the multi-channel light source 1 has n output channels, each channel outputs a light signal of a different frequency, and the light frequencies are υ1, ..., υ n , where the mth channel outputs the light field E m0 (t) can be expressed as:

[0049] E m0 (t) = E0exp[j(ω m t)];

[0050] Where E0 is the light field amplitude, ω m =2πυ m is the angular frequency of the light field.

[0051] Input n channels of RF signals at the same time, where the electric field E of the mth channel RF signal RFm (t) can be expressed as:

[0052]

[0053] Among them, V RFm is the electric field amplitude, ω RFm =2πf m is the electric field angular frequency, is the electric field phase.

[0054] The n phase modulators modulate the n RF input signals into n single-frequency optical signals to complete the electro-optical conversion. The mth phase modulator outputs the optical field E m (t) can be expressed as:

[0055]

[0056] Among them, J n (β m ) represents the nth-order Bessel function; β m is the electro-optical conversion coefficient, V π is the phase modulator half-wave voltage.

[0057] The optical signal output by the phase modulator array 2 is combined by the multi-wavelength optical combiner 3, and the combined optical signal is transmitted to the optical beam splitter 4 through the optical fiber and is divided into two beams of light, one of which is filtered out by the first periodic optical filter 5 to filter out the optical carrier and the upper sideband signal. The optical signal field output by the first periodic optical filter 5 is:

[0058]

[0059] Another optical signal passes through the second periodic optical filter 6 to filter out the optical carrier and the lower sideband signal. The optical signal field output by the second periodic optical filter 6 is:

[0060]

[0061] The optical signals output by the first periodic optical filter 5 and the second periodic optical filter 6 are converted into photoelectric signals by the photosensitive surfaces of the two photodetectors in the balanced photodetector 7, and the output photocurrents of the two paths are:

[0062]

[0063] Where n(t) represents the common-mode noise of the two branches.

[0064] The balanced photodetector 7 receives the two photocurrents differentially, and the output differential current is:

[0065]

[0066] The differential current is subsequently amplified by transimpedance and low-noise amplifiers to output a multi-channel RF signal. From the working principle of the device described above, it can be seen that the device of the present invention can transmit multi-channel RF signals in parallel and suppress common-mode noise n(t) and even-order harmonics during the transmission process. Good transmission performance.

[0067] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A multi-channel optical transmission device based on a periodic optical filter, characterized in that: include: A multi-channel light source (1), located at the transmitting end of the multi-channel light transmission device, and used to output a plurality of light signals of different wavelengths; A phase modulator array (2) is located at the transmitting end of the multi-channel optical transmission device and is used to receive a multi-channel radio frequency input signal and complete the electro-optical conversion of the multi-channel radio frequency input signal to obtain a multi-channel optical signal after the electro-optical conversion; A multi-wavelength optical beam combiner (3), located at the transmitting end of the multi-channel optical transmission device, is used to combine the multi-channel optical signals after optical conversion to obtain a first combined signal; An optical beam splitter (4), located at a receiving end of the multi-channel optical transmission device, is used to receive the first combined beam signal and perform beam splitting processing on the first combined beam signal to obtain a first optical signal and a second optical signal; A first periodic optical filter (5), located at a receiving end of the multi-channel optical transmission device, is used to filter out an optical carrier and an upper sideband signal from the first optical signal to obtain a first output optical signal; A second periodic optical filter (6), located at the receiving end of the multi-channel optical transmission device, is used to filter out the optical carrier and the lower sideband signal from the second optical signal to obtain a second output optical signal; A balanced photodetector (7) is located at the receiving end of the multi-channel optical transmission device and is used to receive the first output optical signal and the second output optical signal, and perform photoelectric conversion and balanced reception on the first output optical signal and the second output optical signal to obtain a multi-channel radio frequency signal.

2. The multi-channel optical transmission device based on periodic optical filter according to claim 1, characterized in that: The multi-channel light source (1) has n output channels, each channel outputs an optical signal, and the wavelengths of the optical signals corresponding to the n output channels are all different, and the difference in optical frequency between adjacent channels in the n output channels is a fixed value Δυ.

3. The multi-channel optical transmission device based on periodic optical filter according to claim 2, characterized in that: The multi-channel light source (1) is specifically a plurality of lasers with different wavelengths.

4. The multi-channel optical transmission device based on periodic optical filter according to claim 2, characterized in that: The multi-channel light source (1) is composed of a single-frequency laser cascade optical micro-ring and an arrayed waveguide grating.

5. The multi-channel optical transmission device based on periodic optical filter according to claim 2, characterized in that: The phase modulator array (2) comprises n phase modulators, and the n phase modulators correspond one-to-one to the n output channels of the multi-channel light source (1).

6. The multi-channel optical transmission device based on periodic optical filter according to claim 1, characterized in that: The multi-wavelength optical beam combiner (3) is an arrayed waveguide grating.

7. The multi-channel optical transmission device based on periodic optical filter according to claim 1, characterized in that: The multi-wavelength optical beam combiner (3) is a wavelength division multiplexer.

8. The multi-channel optical transmission device based on periodic optical filter according to claim 2, characterized in that: The first periodic optical filter (5) is specifically a periodic bandpass filter. The adjacent passband frequency interval of the first periodic optical filter (5) is Δυ, and the first periodic optical filter (5) passes the optical carrier and the upper sideband signal of the input first optical signal and blocks the lower sideband signal.

9. The multi-channel optical transmission device based on periodic optical filter according to claim 2, characterized in that: The second periodic optical filter (6) is specifically a periodic bandpass filter. The adjacent passband frequency interval of the second periodic optical filter (6) is Δυ. The second periodic optical filter (6) passes the optical carrier and the lower sideband signal of the input second optical signal, and blocks the upper sideband signal.

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