TWI515477B - High - speed optical modulation device - Google Patents

Description

High speed optical modulation device

The invention relates to a high-speed optical modulation device, in particular to a high-speed optical modulation device applied to a high-speed backbone network reconfigurable optical plug-in multiplexer transmitting end.

Fiber-optic communication is a way of transmitting information using light and optical fibers. It is a kind of wired communication. Light can carry information after modulation. Optical fiber communication has many advantages such as large transmission capacity and good confidentiality. It has become the most important wired communication method today. In the mode of optical fiber communication, the information to be transmitted is input to the transmitter at the transmitting end, the information is superimposed or modulated onto the carrier as the information signal carrier, and then the modulated carrier is transmitted to the remote receiving end through the transmission medium, The receiver demodulates the original information.

The fiber-optic carrier microwave signal system plays an important role in the future of broadband wireless communication. The microwave signal is converted into an optical signal mainly by using an externally modulated photoelectric modulator. US Patent US 2011/0182590 A1 is composed of multiple Mach-Zehnder (MZM) modulators, which are modulated by 2n-QAM technology. The main applications are 16-QAM and 64-QAM, which are generated by high-order modulation. 100G optical signal. Although this US patent utilizes the new 2n-QAM modulation technology production process to simplify the complexity of its process optoelectronic technology and coding technology, its optical signal characteristics have not been improved. Therefore, the inventor of the present invention aims to design a high-speed optical modulation device capable of converting a signal of 100 Gbit/s or more into an optical signal and simultaneously improving the optical signal transmission quality.

In view of the above prior art problems, it is an object of the present invention to provide a high speed optical modulation device for a reconfigurable optical plug-in multiplexer transmitting end that can be applied to a high speed backbone network.

According to the purpose of the present invention, a high-speed optical modulation device is proposed for high speed The reconfigurable optical plug-in multiplexer transmitter of the backbone network utilizes Polarization Multiplexing Quadrature Phase Shift Keying (PM QPSK) technology and Mach-Zehnder tuning. The transformer converts the electrical signal of Z Gbit/s into an optical signal, and Z is a positive number of 100 or more. The high-speed optical modulation device comprises two pairs of electrical signal modules and one optical modulation module. Each pair of telecommunication modules includes two electric drives and two electric low pass filters. Each of the electric drives is designed with a return-to-zero (RZ) code, and one of the duty cycles is set to a specific value. Each of the electrical low-pass filters is connected to one of the electric drives, and the bandwidth of each of the electrical low-pass filters can be set at Z/4 GHz. The optical modulation module is connected to the two pairs of electrical signal modules to receive a high-rate electrical signal transmitted by each electrical low-pass filter, and is used to convert each high-rate electrical signal into an optical signal. The light modulation module comprises two pairs of optical modulation units, two phase modulators, a light splitter, a polarization rotator and an optical coupler. Each pair of optical modulation units respectively includes two optical modulators, and each optical modulator is connected to one of the electrical low-pass filters. Each phase modulator is connected to one of the optical modulators of each pair of optical modulation units. The optical splitter is connected to each of the optical modulators for receiving continuous laser light. The polarization rotator connects the phase modulator to which one of the pair of optical modulation units is connected and the other of the optical modulators. The optical coupler is connected to a phase modulator connected to one of the other optical modulator units and another optical modulator thereof for connecting the polarization rotator for outputting the optical signal.

Preferably, the specific value of the duty cycle of the return-to-zero code determines the line width of the optical signal.

Preferably, the specific value may be 0.95.

Preferably, each phase modulator sets the driving voltage to V π/2, the engraving signal frequency to 28 GHz, and the phase to π/2 to suppress the side mode from exceeding 8 dB.

Preferably, the number of poles (Pole) of each electrical low-pass filter can be set from 3 to 5.

Preferably, the number of poles of each of the electrical low-pass filters may further be four.

Preferably, each of the electrical low pass filters may be a Bessel filter.

Preferably, each of the optical modulators can be a Mach-Zhande modulator.

As described above, the high-speed optical modulation device of the present invention can pass the electric driver coding, the electrical low-pass filter parameters, and the optical phase modulator and its parameter design, and can be higher than 100 Gbit/s. The speed signal is modulated to the optical signal. Narrowing spectral linewidth can also be achieved in the optical spectrum, and Side mode suppression is suppressed to reduce Dense Wavelength Division Multiplexing (DWDM) channel interference, reduce dispersion, and increase penetration filter tolerance. And other effects.

1A~1D‧‧‧Electric drive

2A~2D‧‧‧Electric low-pass filter

3A~3D‧‧‧Light modulator

4A, 4B‧‧‧ phase modulator

5‧‧‧Light splitter

6‧‧‧Polarization rotator

7‧‧‧Optocoupler

Fig. 1 is a schematic view showing an embodiment of the high-speed optical modulation device of the present invention.

Fig. 2 is a comparison diagram of the modulated light spectrum of the present invention and the original PM QPSK modulated optical spectrum.

Figure 3 is a comparison of the OSNR improvement simulation of the 112 Gbit/s long-haul transmission (DWDM 1800km).

Figure 4 is a comparison of the tolerances of the 112 Gbit/s long-distance transmission multi-order filter tolerance.

The technical features, contents, and advantages of the present invention, as well as the advantages thereof, can be understood by the present inventors, and the present invention will be described in detail with reference to the accompanying drawings. The subject matter is only for the purpose of illustration and description. It is not intended to be a true proportion and precise configuration after the implementation of the present invention. Therefore, the scope and configuration relationship of the attached drawings should not be interpreted or limited. First described.

Please refer to FIG. 1 , which is a schematic diagram of an embodiment of the high-speed optical modulation device of the present invention. In the figure, the high-speed optical modulation device comprises two pairs of electrical signal modules and optical modulation modules. Each pair of electrical signal modules can respectively include two electric drives 1A, 1B and 1C, 1D, and two electric low-pass filters 2A, 2B and 2C, 2D. The optical modulation module can include two pairs of optical modulation units, each of which includes two optical modulators 3A, 3B, and 3C, 3D, and the optical modulation module further includes two phase modulators 4A. And 4B, a light splitter 5, a polarization rotator 6 and an optical coupler 7. The electric low-pass filter 2A is connected to the electric driver 1A and the optical modulator 3A, the electric low-pass filter 2B is connected to the electric driver 1B and the optical modulator 3B, and the electric low-pass filter 2C is connected to the electric driver 1C and the optical adjustment The transformer 3C, the electric low-pass filter 2D is connected to the electric driver 1D and the optical modulator 3D, the optical splitter 5 is connected to the optical modulators 3A, 3B, 3C and 3D, and the phase modulator 4A is connected to the optical modulation. 3B and polarization rotator 6, and polarization rotator 6 is connected to optical modulator 3A and optical coupler 7, phase The bit modulator 4B is connected to the optical modulator 3D and the optical coupler 7, and the optical modulator 3C is connected to the optical coupler 7.

The mating of the above-mentioned modules is only one embodiment, and is not limited thereto.

The high-speed optical modulation device can be mainly applied to a reconfigurable optical plug-in multiplexer transmitting end of a high-speed backbone network, and can utilize Polarization Multiplexing Quadrature Phase Shift Keying (PM-QPSK). Technology and Mach-Zehnder modulators convert electrical signals above 100 Gbit/s into optical signals. Moreover, the high-speed optical modulation device can design the high-speed optical signal spectrum through the Mach-Zhande modulator design and the low-pass filter parameter design, and improve the long-distance transmission of the backbone network and the optical add/drop multiplexer (ROADM). By applying the optical signal transmission quality, the transmission quality can be improved by using a simple method, the transmission distance can be lengthened, and the influence of the multi-order filter can be resisted.

In the above, the optical modulation module is connected to the two pairs of electrical signal modules to receive a high-rate electrical signal transmitted by each of the electrical low-pass filters 2A, 2B, 2C, and 2D, and used to adjust the high-rate electrical signal. Change to an optical signal. Wherein, the plurality of electric drives 1A to 1D are respectively designed with a return-to-zero (RZ) code, and one of the duty cycles of the return-to-zero code is set to a specific value, which determines the line width of the optical signal. Preferably, it is set at 0.95.

Each of the electrical low-pass filters 2A to 2D may be a Bessel filter, and the bandwidth may be set to Z/4 GHz, respectively, and the range of the number of poles (Pole) may be 3 to 5. Where Z is a positive number of 100 or more. Preferably, the bandwidth can be set at 42 GHz and the number of poles can be set to four. Each of the optical modulators 3A to 3D may be a Mach-Zhande modulator, respectively. The driving voltage, the engraving signal frequency, and the phase of each of the phase modulators 4A and 4B can be set to V π/2, 28 GHz, and π/2, respectively. The above values are set for the 100Gbit/s transmitter. These values are only preferred settings and are not limited to this. Among them, the light splitter 5 can be used to receive continuous laser light and distribute the light to the light modulators 3A, 3B, 3C and 3D.

Please refer to FIG. 2 to FIG. 4 together. FIG. 2 is a comparison diagram of the modulated optical spectrum and the original PM-QPSK modulated optical spectrum of the present invention, and FIG. 3 is a long-distance transmission of the present invention at 112 Gbit/s. The OSNR improvement simulation comparison chart (DWDM 1800km) and the fourth picture are the simulation comparison diagrams of the 112 Gbit/s long-distance transmission multi-order filter tolerance. The high-speed optical modulation device architecture of the present invention is divided into an electrical signal module and a light modulation module portion, and the electrical signal module portion can be further divided into electric drives. Encoder design and electrical low pass filter LPF design, where:

1. Electric drive coding design: The return-to-zero (RZ) code is replaced by a special parameter to replace the non-return-to-zero (NRZ) code drive. The duty cycle of the RZ determines the linewidth of the modulated optical signal. The linewidth of the optical signal after RZ coding is wider than that of the NRZ coded optical signal, but can reduce the required optical signal-to-noise ratio (OSNR). ). When the RZ duty cycle is adjusted to 0.95, the line width of the optical signal is similar to the NRZ coded optical signal, but the OSNR can obtain the most margin.

2. Low pass filter (LPF) design: The device's electrical low-pass filter uses a Bessel low-pass filter (Bessel LPF). The smaller the LPF cutoff bandwidth parameter is designed, the smaller the linewidth of the optical spectrum after modulation, but the value is too small, which will cause distortion of the optical signal, which will affect the transmission. Since the Baud Rate is 28 Gbps, if the low-pass filter cut-off frequency is lower than 28 GHz, some signals may be filtered out. The Bessel LPF bandwidth design optimization value can be found through systematic tests. Taking a 100 Gbit/s transmitter as an example, the optimal parameter value may fall near 1.5 times the Baud Rate, which is around 42 GHz. In addition, the number of Pole of Bessel LPF will also affect the line width and transmission distance. Taking a 100 Gbit/s transmitter as an example, the Bessel LPF has an optimized Pole number between 3 and 5.

Regarding the optical modulation module part, it is mainly designed for the optical phase modulator: as shown in Fig. 1, the device needs to add two optical phase modulators. The suppression side mode is achieved by the optical phase modulator driving voltage, the carving signal frequency, the amplitude and the phase design. Through the optical phase modulator design, side mode suppression can be achieved with the addition of some low-light signal line widths. Taking the 100Gbit/s transmitter design as an example, when the phase modulator drive voltage is V π/2, the engraving signal frequency is 28 GHz, and the phase is π/2, the transmitter has the best performance, and the side mode suppression exceeds 8 dB. As shown in Figure 2, the transmission quality and tolerance to multi-level optical filters can be increased.

Take the 112Gbit/s backbone transmission optical modulation device as an example (the packet rate is 28Gbit/s): As shown in Figure 1, the electric drive 1A to the electric drive 1D are all driven by RZ code, and the RZ duty cycle is set. 0.95; the low-pass filter 2A to the low-pass filter 2D use a Bessel low-pass filter, and its bandwidth is set at 42 GHz, and the number of poles is set to 4; the phase modulator 3A and The phase modulator 3B uses a Mach-Zhande modulator whose driving voltage is set to 2.5 volts half of the upper limit of the bias voltage (5 volts), the engraved signal frequency is designed to be 28 GHz, and the bias phase is Set to π/2. The 112 Gbps optical signal generated by the above-mentioned optical modulation device is transmitted by 1800 km in a Dense Wavelength Division Multiplexing (DWDM) system. The simulation results are shown in Figures 3 and 4, and the required optical signal-to-noise ratio is reduced by 0.8 dB when the preFEC (without forward error correction correction) BER is 10-3, and the multi-order filter can be improved. Tolerance to improve delivery quality.

In summary, the high-speed optical modulation device of the present invention can convert an electrical signal of 100 Gbit/s or more into an optical signal without substantially changing the current architecture, and only through the design of the Mach-Zander modulator and the design of the low-pass filter parameters, The optical spectrum is shaped to improve the transmission quality of the backbone network long-distance transmission and optical add/drop multiplexer (ROADM) application, and improve the tolerance of multi-level optical filters and reduce the speed (such as 40G upgrade to 100G) ) Inter-channel interference.

The above is intended to be illustrative only and not limiting. Any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

1A~1D‧‧‧Electric drive

2A~2D‧‧‧Electric low-pass filter

3A~3D‧‧‧Light modulator

4A, 4B‧‧‧ phase modulator

5‧‧‧Light splitter

6‧‧‧Polarization rotator

7‧‧‧Optocoupler

Claims (7)

A high-speed optical modulation device comprises: two pairs of electrical signal modules, each pair of electrical signal modules comprising: two electric drives, respectively designed to have a return-to-zero (RZ) code, the return-to-zero coding One of the duty cycles is set to a specific value that determines the line width of the optical signal; and two electrical low-pass filters are respectively connected to one of the electric drives, and each of the electrical low-pass filters The bandwidth is set at Z/4 GHz, where Z is a positive number of 100 or more; and a light modulation module is connected to the two pairs of electrical signal modules to receive one of the high transmissions of each of the electrical low-pass filters a rate signal for converting the high-rate electrical signals into an optical signal, the optical modulation module comprising: two pairs of optical modulation units, each pair of optical modulation units respectively comprising two optical modulations Each of the optical modulators is respectively connected to one of the electrical low-pass filters; two phase modulators, each of the phase modulators respectively connecting one of the pair of optical modulation units to the optical modulator a light splitter that connects the optical modulators for receiving continuity a laser rotator connected to one of the pair of optical modulation units, the phase modulator connected to the optical modulator and the other of the optical modulators; and an optical coupler Connecting to the phase modulator of the other pair of optical modulation units connected to the optical modulator and the other of the optical modulators, and connecting the polarization rotator to output the optical signal . The high-speed optical modulation device of claim 1, wherein the specific value is 0.95. The high-speed optical modulation device according to claim 1, wherein each of the phase modulators has a driving voltage of V _π /2, an engraving signal frequency of 28 GHz, and a phase of π/2 to suppress the side mode from exceeding 8dB. The high-speed optical modulation device according to claim 1, wherein the range of the number of poles (Pole) of each of the electrical low-pass filters is 3 to 5. The high-speed optical modulation device of claim 4, wherein the number of poles of each of the electrical low-pass filters is four. The high-speed optical modulation device according to claim 1, wherein each of the electrical low-pass filter systems It is a Bessel filter. The high-speed optical modulation device of claim 1, wherein each of the optical modulators is a Mach-Zehnder modulator.