KR20200008709A - Inter-data center interconnects link structure based on pulse amplitude modulation - Google Patents

Abstract

The present invention provides an interconnect link structure between data centers based on pulse width modulation which increases frequency efficiency. The interconnect link structure between data centers comprises: a four-level pulse amplitude modulation (PAM4) generation unit to serialize a multi-channel 400-gigabit non-return-to-zero (NRZ) signal into a PAM4 signal; a light transmitting unit to convert the PAM4 signal which is an electric signal received from the PAM4 generation unit into an optical signal; a light receiving unit to convert the optical signal converted from the light transmitting unit into an electric signal; a PAM4 receiving unit to reverse-serialize the PAM4 signal converted into the electric signal from the light receiving unit into a multi-channel 400-gigabit NRZ signal; and a light transfer unit which is arranged between the light transmitting unit and the light receiving unit, and transfers the optical signal received from the light transmitting unit through optical fiber to the light receiving unit.

Description

Inter-data center interconnects link structure based on pulse amplitude modulation

The present invention relates to a large-capacity optical transmission technology, and more particularly, to a pulse width modulation-based data center that increases frequency efficiency while maintaining an IM / DD (Intensity Modulation & Direct Detection) demodulation scheme based on PAM4 (4-level Pulse Amplitude Modulation). It relates to an interconnect link structure.

Recently, due to the development of Internet technology, data centers are getting bigger and global portal companies are expanding data centers to improve their services. As a result, applications for inter-data center interconnects are attracting attention, and various technical attempts are being made for high-capacity optical transmission.

A 400 gigabit optical-link configuration is required per transceiver, and this is accomplished by using Discrete Multitone (DMT) and Carrierless Amplitude and Phase Modulation, which have higher frequency efficiency than conventional NRZ (Non-Return-to-Zero) methods. Modulation schemes such as Dense Wavelength Division Multiplexing (DWDM) have been attempted.

However, these modulation formats modulate the phase as well as the amplitude of the optical signal and thus cannot use the modulation / modulation method of the existing Intensity Modulation & Eirect Detection (IM / DD) method. That is, additional hardware is required for phase demodulation, which causes a problem of high price and low power efficiency.

Korean Patent Publication No. 10-2012-0081016 (2012.07.18.)

An object of the present invention is to provide an interconnect link structure between pulse width modulation based data centers that improves frequency efficiency while maintaining IM / DD modulation and demodulation through 4 or 8 channel configuration based on PAM4.

In order to achieve the above object, an interconnect link structure between pulse width modulation based data centers according to an embodiment of the present invention is a multi-channel 400 gigabit non-return-to-zero (NRZ) signal. A PAM4 generation unit for serializing a signal, an optical transmitter converting a PAM4 signal received from the PAM4 generator into an optical signal, an optical receiver converting an optical signal converted from the optical transmitter into an electrical signal, and the optical receiver A PAM4 receiver for deserializing a PAM4 signal converted from an electrical signal into a multi-channel 400 gigabit NRZ signal and between the optical transmitter and the optical receiver, and converts the optical signal received from the optical transmitter through the optical fiber to the optical receiver. It includes an optical transmission unit for transmitting.

The PAM4 generation unit may generate a PAM4 signal having 25GBuad × 8 channels or 50GBuad × 4 channels.

In addition, the optical transmitter is characterized by applying a direct modulation or an external modulation method based on the transmission distance.

In addition, the optical transmission unit, if the transmission distance is less than 500m, implemented with a surface emitting laser (Vertical Cavity Surface Emitting Laser, VCSEL), when the transmission distance is 2km to 80km, an external laser or Mach-Zehnder (Mach-Zehnder) Characterized in that implemented with an optical modulator.

In addition, the PAM4 generation unit feeds the serialized PAM4 signal through a feedforward error correction (FEC), and then transmits the PAM4 transmitter to the PAM4 transmitter. After the signal is decoded, the signal is converted into an NZR signal.

In addition, when the transmission distance is less than 500m, the optical transmission unit is characterized in that for transmitting four or eight channels of optical signals in parallel.

The optical transmitter may transmit an optical signal in a wavelength division multiplexing (WDM) method through an optical multiplexer and an optical demultiplexer when the transmission distance is 2 km to 80 km.

According to another embodiment of the present invention, an interconnect link structure based on a pulse width modulation based data center includes a PAM4 generation unit serializing a multi-channel 400 Gigabit NRZ signal into a PAM4 signal, and an optical signal from an PAM4 signal received from the PAM4 generation unit. An optical transmitter for converting the optical signal converted from the optical transmitter into an electrical signal, a PAM4 receiver for deserializing the PAM4 signal converted from the optical receiver into an electrical signal into a multi-channel 400 gigabit NRZ signal, and the optical receiver It is provided between the transmitter and the optical receiver, and transmits the optical signal received from the optical transmitter through the optical fiber to the optical receiver, and the dispersion compensation module (DCM) is provided in the optical fiber and chromatic dispersion (Chromatic Dispersion) It includes a light transmission unit for adjusting).

According to the pulse width modulation-based interconnect link structure of the present invention, PAM4 based interconnect link between 400 Gigabit data centers to improve frequency efficiency while maintaining IM / DD modulation and demodulation method through 8 channels of 25 GBaud per channel or 4 channels of 50 GBaud per channel. The structure can be implemented.

1 is a diagram illustrating a one-channel evaluation setup of a conventional PAM4-based optical link.
2 is a diagram illustrating an interconnect link structure between data centers according to an exemplary embodiment of the present invention.

In the conventional PAM4 based NRZ signal analysis method, as shown in FIG. 1, the PAM4 signal generated by the PAM4 generator and the optical transmitter is converted into an optical signal through an external optical modulator, and the modulated optical signal is converted into an optical signal. Transmit through multiplexer (MUX) In this case, by placing the TDCM (Tunable Dispersion Compensating Module) on the optical path, the degree of chromatic dispersion can be adjusted, and noise is applied from the outside through an ASE (Amplified Spontaneous Emission) noise source. Configure the setup with. Position the Variable Optical Attenuator (VOA) and Erdium-Doped Fiber Amplifier (EDFA) to adjust the receiving optical power, and analyze the output through an Optical Spectrum Analyzer (OSA) to allow color dispersion. Error and ASE noise can be evaluated. The output signal of the optical amplifier is analyzed through the optical demultiplexer (DEMUX) and VOA for the final output NRZ signal through the optical receiver and the PAM4 receiver. This conventional method has a problem of low frequency efficiency and complicated structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention having the above-described problems are improved in detail with reference to the accompanying drawings. First, in adding reference numerals to the components of each drawing, it is noted that the same reference numerals are assigned to the same components as much as possible even if displayed on different drawings. In addition, in describing the present invention, when a detailed description of a related well-known configuration or function is apparent to those skilled in the art or may deny the gist of the present invention, the detailed description thereof will be omitted.

2 is a diagram illustrating an interconnect link structure between data centers according to an exemplary embodiment of the present invention.

Referring to FIG. 2, an interconnect link structure (hereinafter, referred to as a 'link structure') 100 between data centers may increase frequency efficiency while maintaining an IM / DD modulation / demodulation scheme through 4-channel or 8-channel configuration based on PAM4. have. The link structure 100 includes a PAM4 generator 10, an optical transmitter 20, an optical transmitter 30, an optical receiver 40, and a PAM4 receiver 50.

The PAM4 generation unit 10 receives a multi-channel 400 gigabit NRZ signal, converts the input NRZ signal into a PAM4 signal, and serializes it. Here, the multi-channel 400 gigabit NRZ signal may be input in various ways such as 10 Gb / s × 40 channels, 25 Gb / s × 16 channels, 50 Gb / s × 8 channels, and the like. The PAM4 generation unit 10 includes a serialization module 11, a plurality of FEC transmission modules 12, and a plurality of PAM4 transmission modules 13. The number of FEC transmission modules 12 and PAM4 transmission modules 13 is designed to correspond to the number of channels of serialized PAM4 signals.

The serialization module 11 receives a multi-channel 400 gigabit NRZ signal and converts the NRZ signal into a PAM4 signal. The serialization module 11 serializes the converted PAM4 signal. The serialization module 11 generates a PAM4 signal having 25 GB uad x 8 channels or 50 GB uad x 4 channels for a transmission capacity of 400 gigabit. Here, the 25GBuad PAM4 signal has the same transmission capacity as the NRZ signal of 50Gb / s and is composed of 8 channels to enable 400 gigabit transmission, and the 50GBuad PAM4 signal has the same transmission capacity as the NRZ signal of 100Gb / s and 4 Channels can be configured for 400 Gigabit transmission.

The FEC transmission module 12 encodes the serialized PAM4 signal by Feedforward Error Correction (FEC) and transmits it to the PAM4 transmission module 12. Through this, the PAM4 signal may be transmitted to the PAM4 transmission module 12 with the error minimized.

The PAM4 transmission module 12 transmits the FEC-coded PAM4 signal from the FEC transmission module 11 to the optical transmitter 20.

The optical transmitter 20 converts the PAM4 signal received from the PAM4 generator 10 into an optical signal. The optical transmitter 20 includes a plurality of optical transmitters 21. The number of optical transmitters 21 is designed to correspond to the number of channels of the PAM4 signal. The optical transmitter 21 may apply both a direct modulation method or an external modulation method based on a transmission distance and an application of an optical link.

For example, when the transmission distance is shorter than 500m, the optical transmitter 21 may be implemented as a low-cost device such as a vertical cavity surface emitting laser (VCSEL). In addition, when the transmission distance is 2km to 80km long, the optical transmitter 21 may be implemented as an external modulator such as an external laser or a Mach-Zehnder optical modulator.

The optical transmitter 30 is provided between the optical transmitter 20 and the optical receiver 40. The optical transmitter 30 transmits the optical signal received from the optical transmitter 20 through the optical fiber 33 to the optical receiver 40. The optical transmitter 30 includes an optical fiber 33, and further includes an optical multiplexer 31, an optical demultiplexer 32, a dispersion compensating module (DCM) 34, and an amplifier.

The optical transmitter 30 determines whether the optical multiplexer 31 and the optical demultiplexer 32 are included according to the transmission distance.

For example, when the transmission distance is shorter than 500m, the optical transmitter 30 may transmit optical signals of four or eight channels in parallel. As described above, when the optical signal is transmitted in a parallel structure of 4 channels or 8 channels, the optical transmitter 30 may not include the optical multiplexer 31 and the optical demultiplexer 32.

When the transmission distance is 2km to 80km long, the optical transmitter 30 may transmit an optical signal through a wavelength division multiplexing (WDM) method through the optical multiplexer 31 and the optical demultiplexer 32. The optical transmission unit 30 may improve the price competitiveness by serializing four or eight wavelengths according to the number of channels of the PAM4 signal and transmitting them to one optical fiber 33. That is, the optical transmitter 30 may reduce the number of optical fibers 33 by using the optical multiplexer 31 and the optical demultiplexer 32. Here, the optical transmitter 30 may include an amplifier at an output terminal of the optical multiplexer 31 and an input terminal of the optical demultiplexer 32 to amplify the optical signal.

In addition, the optical transmission unit 30 may include a DCM 34 in the optical fiber 33 to adjust chromatic dispersion. This allows us to evaluate color dispersion tolerance, an important parameter for link performance in 400 Gigabit optical links.

The optical receiver 40 linearly converts the optical signal converted from the optical transmitter 20 into an electrical signal. At this time, the light receiving unit 40 receives the 4 or 8 channel optical signal transmitted from the light transmitting unit 30 as an electrical signal. To this end, the optical receiver 40 includes a plurality of optical receivers 41. The number of optical receivers 41 is designed to correspond to the number of channels of the PAM4 signal. Here, the optical receiver 41 may include a photodetector and a linear amplifier.

The PAM4 receiver 50 converts the PAM4 signal converted from the optical receiver 40 into an electrical signal into a multi-channel 400 gigabit NRZ signal and outputs the converted signal. The PAM4 receiving unit 50 includes a plurality of PAM4 receiving modules 51, a plurality of inverse FEC receiving modules 52, and a deserializing module 53. The number of PAM4 receiving module 51 and the inverse FEC receiving module 52 is designed to correspond to the number of channels of the received PAM4 signal.

The PAM4 receiving module 51 transmits the PAM4 signal received from the optical receiving unit 40 to the inverse FEC receiving module 52.

The inverse FEC receiving module 52 decodes the FEC-coded PAM4 signal from the PAM4 generation unit 10 and transmits the decoded PAM4 signal to the deserialization module 53.

Deserialization module 53 converts the PAM4 signal to an NRZ signal and deserializes it. To this end, the deserialization module 53 may include a clock-and-data recovery circuit. In other words, the deserialization module 53 outputs a multi-channel 400 gigabit NRZ signal.

As described above, the present invention can implement an interconnect link structure between 400 Gigabit data centers to improve frequency efficiency while maintaining IM / DD modulation and demodulation scheme through 8 channels of 25GBaud per channel or 4 channels of 50GBaud based on PAM4. In addition, the present invention can improve the price competitiveness by reducing the number of optical fibers by applying the wavelength division multiplexing technology to the optical transmission process.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific preferred embodiments described above, and the present invention belongs to the present invention without departing from the gist of the present invention as claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

10: PAM4 generator
11: serialization module
12: FEC transmission module
13: PAM4 sending module
20: optical transmission unit
21: optical transmitter
30: optical transmission unit
31: optical multiplexer
32: optical demultiplexer
33: optical fiber
34: Distributed Compensation Module
40: light receiving unit
41: optical receiver
50: PAM4 receiver
51: PAM4 receiving module
52: reverse FEC receiving module
53: deserialization module
100: interconnect link structure between data centers

Claims (8)

A PAM4 generation unit for serializing a multi-channel 400 gigabit Non-Return-to-Zero (NRZ) signal into a 4-level pulse amplitude modulation (PAM4) signal;
An optical transmitter converting the PAM4 signal received from the PAM4 generator into an optical signal;
An optical receiver converting the optical signal converted from the optical transmitter into an electrical signal;
A PAM4 receiver for deserializing the PAM4 signal converted from the optical receiver into an electrical signal into a multi-channel 400 gigabit NRZ signal; And
An optical transmitter provided between the optical transmitter and the optical receiver and transmitting an optical signal received from the optical transmitter to the optical receiver through an optical fiber;
Interconnect link structure between the pulse width modulation-based data center comprising a. The method of claim 1,
The PAM4 generation unit,
A pulse width modulation based inter-data center interconnect link structure, characterized by generating a PAM4 signal having 25GBuad × 8 channels or 50GBuad × 4 channels. The method of claim 1,
The optical transmitter,
A pulse width modulation-based interconnect link structure between data centers, characterized by applying a direct modulation or an external modulation based on a transmission distance. The method of claim 3, wherein
The optical transmitter,
If the transmission distance is less than 500m, it is implemented by a surface emitting laser (Vertical Cavity Surface Emitting Laser, VCSEL),
When the transmission distance is 2km to 80km, the interconnect link structure between the pulse width modulation-based data center, characterized in that implemented as an external laser or a Mach-Zehnder optical modulator. The method of claim 1,
The PAM4 generation unit,
The serialized PAM4 signal is subjected to Feedforward Error Correction (FEC) coding, and then transmitted to the PAM4 transmitter.
The PAM4 receiver,
The PAM4 generation unit reverse-codes the feedforward error correction coded PAM4 signal, and then converts the PAM4 signal into an NZR signal. The method of claim 1,
The optical transmission unit,
If the transmission distance is less than 500m, the pulse width modulation-based interconnect link structure between the four-channel or eight-channel optical signal, characterized in that for transmitting in parallel. The method of claim 1,
The optical transmission unit,
The pulse width modulation-based interconnect link structure, characterized in that for transmitting the optical signal in a wavelength division multiplexing (WDM) method through the optical multiplexer and optical demultiplexer when the transmission distance is 2km to 80km. A PAM4 generation unit for serializing a multi-channel 400 gigabit NRZ signal into a PAM4 signal;
An optical transmitter converting the PAM4 signal received from the PAM4 generator into an optical signal;
An optical receiver converting the optical signal converted from the optical transmitter into an electrical signal;
A PAM4 receiver for deserializing the PAM4 signal converted from the optical receiver into an electrical signal into a multi-channel 400 gigabit NRZ signal; And
The optical transmitter is provided between the optical transmitter and the optical receiver, and transmits an optical signal received from the optical transmitter through the optical fiber to the optical receiver, and includes a dispersion compensating module (DCM) in the optical fiber to provide color dispersion ( An optical transmission unit for adjusting chromatic dispersion;
Interconnect link structure between the pulse width modulation-based data center comprising a.

Images