JP2016005193A - Optical access system, terminator, home device and optical access method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system achieving economical high speed large capacity and flexible adaptive modulation, without complicating the configuration and without making the device expensive, in a time sharing multiplex access system and/or wavelength multiplex access system.SOLUTION: A PAM adaptive modulation OLT3 performs PAM modulation of multiple value greater than binary having a multiple value level depending on the transmission distance, for a downlink signal transmitted to an ONU4, and PAM modulation of multiple value greater than binary having a multiple value level depending on the transmission distance, for an uplink signal received from the ONU4. The ONU4 performs PAM demodulation of multiple value greater than binary having a multiple value level depending on the transmission distance, for a downlink signal received from the PAM adaptive modulation OLT3, and PAM modulation of multiple value greater than binary having a multiple value level depending on the transmission distance, for an uplink signal transmitted to the PAM adaptive modulation OLT3.

Description

  The present invention relates to a technique for realizing economical high-speed and large-capacity and flexible adaptive modulation in a time division multiplexing optical access system and / or wavelength division multiplexing optical access system.

  In recent years, the introduction of a Passive Optical Network (PON) system has been promoted in various countries around the world as an optical access system that supports the Fiber To The Home (FTTH) service, which has been rapidly spreading.

  The PON system is an in-home device in which one terminal device (OLT: Optical Line Terminal) installed in a receiving station is installed in a plurality of subscriber homes via an optical splitter installed in an optical fiber transmission line. By accommodating an (ONU: Optical Network Unit), an optical access system that realizes high economic efficiency by sharing an optical fiber transmission line, an optical splitter, and an OLT among a plurality of subscribers.

  Currently, in Japan, a GE-PON (Gigabit Ethernet-PON) system mainly having a transmission rate of 1 Gb / s has been introduced commercially (Ethernet is a registered trademark). In addition, NG-PON2 (10 G-EPON (10 Gigabit-Ethernet PON) system, which increases the signal speed by 10 times, and wavelength division multiplexing (WDM) technology to realize 40G-class transmission capacity ( Next Generation-PON2) system is being standardized and researched and developed (for example, see Non-Patent Document 1).

H. Nakamura, K .; Taguchi, S .; Tamaki, T .; Mizuno, Y.M. Hashizumi, T .; Yamada, M .; Ito, H .; Takahashi, S .; Kimura, and N.K. Yoshimoto, “40 Gbit / s-class-λ-tunable WDM / TDM-PON using λ-selectable B-Tx and 4 × M cyclic AWG route for Oregonet” 21, no. 1, pp. 463-468, January 2013. N. Iiyama, JI. Kani, J. et al. Terada, and N.A. Yoshimoto, “Feasibility Study on a Scheme for Coexistence of DSP-Based PON and 10-Gbps / λ PON Using Hierarchical Star QAM Format.” Journal of Japan. 31, no. 4, pp. 3085-3092, 2013. Cvjetic. N, “OFDM for Next-Generation Optical Access Networks,” Journal of lightwave technology, Vol. 30, no. 4, pp. 384-398, 2012.

  In recent years, studies have been conducted to realize high-speed and large-capacity systems, and studies to increase system flexibility have been actively conducted, especially according to transmission path quality and required transmission quality. An adaptive modulation technique that optimizes a modulation scheme and a bit rate of a signal assigned to each user has attracted attention (see, for example, Non-Patent Document 2).

  The configuration of a conventional optical access system is shown in FIG. The optical access system of the prior art is a PON using a QAM (Quadrature Amplitude Modulation) method and adaptive modulation technology, QAM adaptive modulation OLT1 installed in a communication carrier building, ONU2-1-1 installed in a user's home ..., 2-1-m, 2-2-1, ..., 2-2m, ..., 2-n-1, ..., 2-nm, the optical signal. It comprises an optical splitter that multiplexes and demultiplexes, and an optical fiber that is a transmission path.

  The QAM adaptive modulation OLT1 determines the format of the uplink signal and the downlink signal according to the transmission path quality and required transmission quality of each ONU2. Basically, the signal multiplicity increases, and the signal-to-noise ratio of the signal deteriorates, so that the signal transmission distance is limited.

  The formats of the prior art upstream burst signal and downstream continuous signal are shown in FIGS. 2 and 3, only the ONUs 2-1-1, 2-1 and 2-n-1 are shown. Since the ONU 2-1-1 is at a short distance from the QAM adaptive modulation OLT 1, the upstream burst signal from the ONU 2-1-1 and the downstream continuous signal to the ONU 2-1-1 are 16QAM signals having a large multilevel value. . Since ONU2-2-1, 2-n-1 is far from QAM adaptive modulation OLT1, upstream burst signals from ONU2-2-1, 2-n-1 and ONU2-2-1, 2-n-1 The downstream continuous signal to −1 is a 4QAM signal having a small multilevel value.

  As described with reference to FIGS. 1 to 3, many applied modulation techniques using a QAM modulation method have been reported, but an NRZ (Non Return to Zero) signal of an OOK (On Off Keying) modulation method is used. No one has been reported for use. Compared with the one using the QAM modulation method and the like using the NRZ signal of the OOK modulation method, the transmission speed capable of realizing high economic efficiency is about 10 Gb / s mainly due to the operation limitation of the electric circuit for controlling the optical device. This is because there is a problem that is limited.

  On the other hand, OFDM (Orthogonal Frequency Division Multiplexing) technology applied in wireless technology and digital signal processing (DSP: Digital Signal Processing) as future optical communication systems that realize dramatic speedup, large capacity, and sophistication. ) And a technology applied to long-distance large-capacity optical communication, such as a digital coherent technology combined with a coherent technology, has been studied (for example, see Non-Patent Document 3).

  In OFDM-PON and digital coherent PON, it is possible to drastically increase the speed, capacity, and sophistication of the system. However, OFDM-PON requires a light source with a narrow line width and high transmission stability, and digital coherent PON requires a coherent transceiver, a digital-analog conversion circuit for digital signal processing, and a signal processing calculation circuit. . Therefore, OFDM-PON and digital coherent PON have a problem in that it is difficult to make the system economical because the configuration is complicated and the device is expensive.

  Accordingly, in order to solve the above-mentioned problems, the present invention provides an economical high-speed and large-capacity configuration in a time division multiplexing optical access system and / or wavelength multiplexing optical access system without complicating the configuration and making the device expensive. And it aims at realizing flexible adaptive modulation.

  In order to achieve the above object, by using a multi-value pulse intensity modulation (PAM) method in which the multi-value degree is determined in accordance with the transmission distance, the number of uplink signals and / or downlink signals is increased. It was decided to improve the value.

  Specifically, the present invention is an optical access system comprising a terminal device and a plurality of home devices, wherein the terminal device transmits a downlink signal transmitted to the home device to the home device. Multi-value pulse intensity modulation with a multi-value greater than two values determined according to the distance and an uplink signal received from the home device greater than a binary value with a multi-value determined according to the transmission distance from the home device One or both of multi-level pulse intensity demodulation is performed, and the in-home device is larger than a binary value whose multi-level is determined according to a transmission distance from the terminal device with respect to a downlink signal received from the terminal device One of a multi-level pulse intensity demodulation and a multi-level pulse intensity modulation larger than two values, the multi-level of which is determined according to the transmission distance to the terminal device, for an upstream signal transmitted to the terminal device. Both an optical access system and performs.

  In addition, the present invention is a terminal device that communicates with a home device in an optical access system, and a binary value that has a multi-value degree determined according to a transmission distance to the home device with respect to a downlink signal transmitted to the home device A multi-level modulation unit that performs larger multi-level pulse intensity modulation, and a multi-level pulse intensity that is greater than two values, the multi-level of which is determined according to the transmission distance from the in-home device, with respect to the uplink signal received from the in-home device A termination device comprising one or both of a multi-level demodulator for performing demodulation.

  Further, the present invention is an in-home device that communicates with a termination device in an optical access system, and is based on a binary value that determines a multilevel degree according to a transmission distance from the termination device for a downlink signal received from the termination device A multi-level demodulating unit that demodulates a large multi-level pulse intensity, and a multi-level pulse intensity that is greater than a binary value that has a multi-level determined in accordance with a transmission distance to the terminal device for an uplink signal transmitted to the terminal device An in-home apparatus comprising one or both of a multi-level modulation unit that performs modulation.

  The present invention is also an optical access method using a terminal device and a plurality of home devices, wherein the terminal device responds to a downlink signal transmitted to the home device according to a transmission distance to the home device. Multi-level pulse intensity modulation is performed that is greater than the binary value that determines the multi-level value, and the multi-level value is determined according to the transmission distance from the terminal device to the downlink signal received by the home device from the terminal device 2 A downlink signal modulation / demodulation step for performing multi-value pulse intensity demodulation larger than the value, and a binary value whose multivalue level is determined in accordance with a transmission distance to the terminal device for an upstream signal transmitted from the home device to the terminal device Multi-level pulse intensity modulation is performed, and the termination device is a multi-value greater than two values with which the multi-level degree is determined according to the transmission distance from the home device with respect to the upstream signal received from the home device. An optical access method and performing an uplink signal demodulation step of performing a pulse intensity demodulation, one or both of the.

  According to this configuration, since a multi-value PAM system that is larger than binary is used without using an OOK modulation system, a higher speed and a larger capacity can be achieved than a simple OOK modulation system, and OFDM technology or digital coherent can be used. From the technology, it is possible to achieve economy, and thus it is possible to realize economical high speed and large capacity and flexible adaptive modulation.

  Here, if a multi-value PAM system larger than binary is used based on the existing OOK modulation system, an existing optical device or electronic circuit can be applied. Therefore, economical high-speed / large capacity and flexible Adaptive modulation can be realized.

  The present invention is also an optical access system comprising a termination device and a plurality of in-home devices, wherein the termination device responds to a transmission distance to the in-home device for a downlink signal transmitted to the in-home device. The multi-value level is determined in accordance with one of multi-value pulse intensity modulation and binary on-off modulation larger than the binary value, and the transmission distance from the home device for the uplink signal received from the home device. One or both of multi-level pulse intensity demodulation and binary on / off demodulation larger than a predetermined binary value are performed, and the in-home device transmits a downlink signal received from the end device to the end device. One of multi-level pulse intensity demodulation and binary on-off demodulation greater than binary, the multi-level of which is determined according to the distance, and the end signal for the upstream signal transmitted to the end device. An optical access system that performs one or both of multi-level pulse intensity modulation and binary on-off modulation greater than binary, the multi-level of which is determined according to the transmission distance to the apparatus. .

  According to this configuration, since an OOK modulation method and a multi-value PAM method larger than two values are used, higher speed and larger capacity can be achieved than a simple OOK modulation method, and OFDM technology and digital coherent technology can be achieved. Thus, the economy can be improved, and therefore, economical high speed and large capacity and flexible adaptive modulation can be realized.

  Here, if a multi-value PAM system larger than binary is used based on the existing OOK modulation system, an existing optical device or electronic circuit can be applied. Therefore, economical high-speed / large capacity and flexible Adaptive modulation can be realized.

  Further, the present invention provides a modulation that has a maximum multilevel value that is determined according to a transmission distance to the in-home device, and does not deteriorate a signal-to-noise ratio, with respect to a downlink signal transmitted to the in-home device. The uplink signal received from the in-home device is determined according to a transmission distance from the in-home device, and has a maximum multi-level that does not deteriorate the signal-to-noise ratio, and one or both of the demodulation, , With respect to the downlink signal received from the termination device, the demodulation having the maximum multi-level that is determined according to the transmission distance from the termination device and does not deteriorate the signal-to-noise ratio, and for the uplink signal transmitted to the termination device, One or both of modulation and modulation having the maximum multi-level that is determined according to the transmission distance to the terminating device and does not degrade the signal-to-noise ratio. Is Temu.

  According to this configuration, the PAM signal or the OOK signal can be transmitted / received with the maximum multi-level that is determined according to the transmission distance and does not deteriorate the signal-to-noise ratio.

  Further, the present invention provides a modulation in which the termination device has a multi-value degree determined according to a transmission distance to the in-home device and a communication band to the in-home device for a downlink signal transmitted to the in-home device, The uplink signal received from the in-home device performs one or both of a demodulation having a multi-value level determined according to a transmission distance from the in-home device and a communication band from the in-home device, and the in-home device Demodulation having a multilevel value determined according to a transmission distance from the termination device and a communication band from the termination device with respect to a downlink signal received from the termination device, and the termination device with respect to an uplink signal transmitted to the termination device An optical access system that performs one or both of modulation having a multi-value level determined according to a transmission distance to the terminal device and a communication band to the termination device

  According to this configuration, the PAM signal or the OOK signal can be transmitted / received with a multi-value degree determined according to both the transmission distance and the communication band.

  In the present invention, the transmission distance between the terminating device and the in-home device is estimated by the terminating device based on ranging information when the terminating device performs dynamic bandwidth allocation to the in-home device. An optical access system is characterized.

  According to this configuration, the transmission distance can be easily estimated.

  As described above, the present invention provides an economical high-speed, large-capacity and flexible adaptive modulation in a time-division multiplexed optical access system and / or a wavelength-multiplexed optical access system without complicating the configuration and making the device expensive. Can be realized.

It is a figure which shows the structure of the optical access system of a prior art. It is a figure which shows the format of the upstream burst signal of a prior art. It is a figure which shows the format of the downlink continuous signal of a prior art. 1 is a diagram illustrating a configuration of an optical access system according to a first embodiment. It is a figure which shows the format of the upstream burst signal of Embodiment 1. It is a figure which shows the format of the downstream continuous signal of Embodiment 1. FIG. FIG. 3 is a diagram illustrating a configuration of a PAM adaptive modulation OLT according to the first embodiment. It is a figure which shows the production | generation method of the downlink continuous signal of Embodiment 1. FIG. It is a figure which shows the structure of ONU of Embodiment 1. FIG. It is a figure which shows the structure of the optical access system of Embodiment 2. FIG. It is a figure which shows the format of the upstream burst signal of Embodiment 2. It is a figure which shows the format of the continuous downlink signal of Embodiment 2. 6 is a diagram illustrating a configuration of a PAM adaptive modulation OLT according to a second embodiment. FIG. It is a figure which shows the production | generation method of the downlink continuous signal of Embodiment 2. FIG. It is a figure which shows the structure of ONU of Embodiment 2. FIG. FIG. 10 is a diagram illustrating a configuration of an optical access system according to a third embodiment. It is a figure which shows the structure of the optical access system of Embodiment 4.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
FIG. 4 shows the configuration of the optical access system according to the first embodiment. The optical access system according to the first embodiment is a PON that uses a PAM system and adaptive modulation technology, and includes a PAM adaptive modulation OLT 3 installed in a communication carrier building, an ONU 4-1-1 installed in a user's house,. , 4-1-m, 4-2-1,..., 4-2-2m,..., 4-n-1,. It is composed of an optical splitter and an optical fiber as a transmission path.

  The PAM adaptive modulation OLT 3 determines the format of the uplink signal and the downlink signal according to the transmission path quality and required transmission quality of each ONU 4. Basically, the signal multiplicity increases, and the signal-to-noise ratio of the signal deteriorates, so that the signal transmission distance is limited.

  In FIG. 4, the PAM adaptive modulation OLT 3 includes the ONUs 4-1-1,..., 4-1-m, 4-n−1,..., 4-n-m that are close to the PAM adaptive modulation OLT 3. And it is determined that it is in an area where the PAM8 signal can be applied. In addition, the PAM adaptive modulation OLT 3 is located in an area where ONU 4-2-1,..., 4-2-m are far from the PAM adaptive modulation OLT 3, and the PAM 8 signal cannot be applied and the PAM 4 signal can be applied. Judge that.

  The PAM adaptive modulation OLT 3 is a multi-value PAM modulation having a multi-value larger than a binary value determined according to a transmission distance to each ONU 4 with respect to a continuous downlink signal transmitted to each ONU 4, and an upstream burst signal received from each ONU 4. On the other hand, multi-value PAM demodulation having a multi-value greater than two values, in which the multi-value degree is determined according to the transmission distance from each ONU 4, is performed.

  Here, when performing PAM modulation, the PAM adaptive modulation OLT 3 is determined according to the transmission distance to each ONU 4 with respect to the downstream continuous signal transmitted to each ONU 4 and has the maximum multilevel value that does not deteriorate the signal-to-noise ratio. Modulation. The PAM adaptive modulation OLT 3 is a demodulator having a maximum multilevel value that is determined according to the transmission distance from each ONU 4 and does not deteriorate the signal-to-noise ratio with respect to the upstream burst signal received from each ONU 4 when performing PAM demodulation. I do.

  Each ONU 4 transmits, to the PAM adaptive modulation OLT 3, a multi-value PAM demodulation having a multi-value greater than a binary value, the multi-value degree of which is determined according to the transmission distance from the PAM adaptive modulation OLT 3 with respect to the downlink continuous signal received from the PAM adaptive modulation OLT 3. The multi-level PAM modulation is performed with respect to the upstream burst signal to be larger than the binary value in which the multi-level degree is determined according to the transmission distance to the PAM adaptive modulation OLT 3.

  Here, when each ONU 4 performs PAM demodulation, the maximum multilevel value that is determined according to the transmission distance from the PAM adaptive modulation OLT 3 to the downlink continuous signal received from the PAM adaptive modulation OLT 3 and does not deteriorate the signal-to-noise ratio. Is demodulated. Each of the ONUs 4 is determined according to the transmission distance to the PAM adaptive modulation OLT 3 with respect to the upstream burst signal transmitted to the PAM adaptive modulation OLT 3 when performing the PAM modulation. Modulation is performed.

  The transmission distance between the PAM adaptive modulation OLT 3 and each ONU 4 is estimated by the PAM adaptive modulation OLT 3 based on the ranging information when the PAM adaptive modulation OLT 3 performs dynamic band allocation to each ONU 4. Therefore, the transmission distance can be easily estimated.

  The formats of the upstream burst signal and downstream continuous signal according to the first embodiment are shown in FIGS. 5 and 6 show only the ONUs 4-1 -m, 4-2 -m, and 4-n -m. The ONUs 4-1m and 4-nm are in an area where the PAM8 signal can be applied, and the maximum multi-level is adopted among the allowable multi-levels, and the upstream burst signal and the downstream continuous signal have the light intensity. Is a PAM8 signal that is modulated in eight stages of “0”, “1”, “2”, “3”, “4”, “5”, “6”, “7”. The ONU 4-2-m is in an area to which the PAM 4 signal can be applied, and the maximum multi-level is adopted among the allowable multi-levels. The upstream burst signal and the downstream continuous signal have a light intensity of “0”, “ This is a PAM4 signal modulated in four stages of “1”, “2”, and “3”.

  FIG. 7 shows the configuration of the PAM adaptive modulation OLT according to the first embodiment. The PAM adaptive modulation OLT 3 includes a multi-level modulation unit 31 and a multi-level demodulation unit 32.

  The multi-level modulation unit 31 synthesizes the outputs of two or three OOKs, and thereby multi-value (in this case, 4-value and 8-value) PAM for the downstream continuous signal transmitted to each ONU 4. Modulate. The multi-level demodulator 32 performs PAM demodulation of multi-values (in this case, 4-value and 8-value) larger than binary on the upstream burst signal received from each ONU 4.

  The multilevel modulation unit 31 includes electrical signal generation units 311, 312, 313, a signal generation unit control unit 314, an electrical signal synthesis unit 315, and an optical signal generation unit 316. According to the signal generation method, the PAM4 signal and the PAM8 signal are generated.

  The electric signal generator 311 generates an electric signal of “0” level or “1” level. The electric signal generator 312 generates an electric signal of “0” level or “2” level. The electrical signal generator 313 generates an electrical signal of “0” level or “4” level. The signal generation unit control unit 314 controls the electric signal generation units 311, 312, and 313 to generate which one of the electric signals that can be generated.

  The electrical signal synthesis unit 315 receives one of the electrical signals that can be generated from each of the electrical signal generation units 311, 312, and 313, and synthesizes the input electrical signals. The optical signal generation unit 316 receives the combined electric signal from the electric signal combining unit 315, and directly modulates the laser itself or externally modulates the continuous optical signal based on the input combined electric signal. , PAM4 signal and PAM8 signal are generated.

  The configuration of the ONU of Embodiment 1 is shown in FIG. The ONU 4 includes a multilevel modulation unit 41 and a multilevel demodulation unit 42. The multi-level modulation unit 41 synthesizes the outputs of two or three OOK, thereby multi-level (in this case, 4-level or 8-level) greater than 2 for the upstream burst signal transmitted to the PAM adaptive modulation OLT 3 PAM modulation is performed. The multi-level demodulator 42 performs multi-level (four-level or 8-level) PAM demodulation larger than binary on the downlink continuous signal received from the PAM adaptive modulation OLT 3.

  The multi-level modulation unit 41 includes an electric signal generation unit 411, 412, 413, a signal generation unit control unit 414, an electric signal synthesis unit 415, and an optical signal generation unit 416. Similar to the signal generation method, the PAM4 signal or the PAM8 signal is generated.

  In the first embodiment, since a multi-value PAM system larger than binary is used without using an OOK modulation system, it is possible to achieve a higher speed and a larger capacity than a simple OOK modulation system, and an OFDM technique or a digital coherent technique. Thus, the economy can be improved, and therefore, economical high speed and large capacity and flexible adaptive modulation can be realized.

  In the first embodiment, since the multi-value PAM method larger than the binary value is used based on the existing OOK modulation method, an existing optical device or electronic circuit can be applied. And flexible adaptive modulation can be realized.

  Furthermore, in the first embodiment, a PAM signal or an OOK signal can be transmitted / received with the maximum multi-level that is determined according to the transmission distance and does not degrade the signal-to-noise ratio.

  Here, in the first embodiment, a multi-value PAM scheme that is larger than binary is used for both the upstream burst signal and the downstream continuous signal. On the other hand, as a modification, a multi-value PAM scheme larger than binary may be used for one of the upstream burst signal and the downstream continuous signal.

In the first embodiment, a 4-value and 8-value PAM method is used. On the other hand, as a modified example, a multi-value PAM method larger than 4-value and 8-value may be used. Here, when the ^2n- value PAM method is used, an electric signal generation unit that generates an electric signal of “0” level or “1” level, and an electric signal that generates an electric signal of “0” level or “2” level. A signal generator,..., An electric signal generator that generates an electric signal of “0” level or “2 ⁿ⁻¹ ” level may be arranged.

  Furthermore, in Embodiment 1, a TDM-PON is configured using an optical splitter. On the other hand, as a modification, WDM-PON or TDM / WDM-PON may be configured by using AWG (Arrayed Waveguide Grating).

(Embodiment 2)
The configuration of the optical access system of the second embodiment is shown in FIG. The optical access system according to the second embodiment is a PON that uses a PAM system, an OOK modulation system, and an adaptive modulation technique, and includes a PAM adaptive modulation OLT 5 installed in a telecommunications carrier building and an ONU 6-1-1 installed in a user's home. ,..., 6-1-m, 6-2-1,..., 6-2-m,..., 6-n-1,. It comprises an optical splitter that multiplexes and demultiplexes and an optical fiber that is a transmission path.

  The PAM adaptive modulation OLT 5 determines the format of the uplink signal and the downlink signal according to the transmission path quality and required transmission quality of each ONU 6. Basically, the signal multiplicity increases, and the signal-to-noise ratio of the signal deteriorates, so that the signal transmission distance is limited.

  In FIG. 10, the PAM adaptive modulation OLT 5 determines that the ONUs 6-1-1,..., 6-1 -m are in a short distance from the PAM adaptive modulation OLT 5 and are in an area where the PAM 8 signal can be applied. . In the PAM adaptive modulation OLT 5, the ONUs 6-n-1,..., 6-nm are located at a medium distance from the PAM adaptive modulation OLT 5, and the PAM 8 signal cannot be applied and the PAM 4 signal can be applied. Judge that. Further, the PAM adaptive modulation OLT 5 has ONU 6-2-1,..., 6-2-m at a long distance from the PAM adaptive modulation OLT 5, and can apply the NRZ signal without applying the PAM 8 signal and the PAM 4 signal. Judged to be in the area.

  The PAM adaptive modulation OLT 5 is one of a multi-value PAM modulation and a binary OOK modulation larger than a binary value whose multi-value degree is determined according to a transmission distance to each ONU 6 with respect to a downstream continuous signal transmitted to each ONU 6. For the upstream burst signal received from each ONU 6, either multi-value PAM demodulation or binary OOK demodulation that is greater than binary and whose multi-value is determined according to the transmission distance from each ONU 6 is performed.

  Here, the PAM adaptive modulation OLT 5 is determined according to the transmission distance to each ONU 6 with respect to the continuous downlink signal transmitted to each ONU 6 when performing PAM modulation and OOK modulation. Modulation having a degree of value is performed. The PAM adaptive modulation OLT 5 determines the maximum multi-level that is determined according to the transmission distance from each ONU 6 and does not deteriorate the signal-to-noise ratio with respect to the upstream burst signal received from each ONU 6 when performing PAM demodulation and OOK demodulation. Is demodulated.

  Each ONU 6 has either a multi-value PAM demodulation or a binary OOK demodulation larger than a binary value, the multi-value degree of which is determined according to the transmission distance from the PAM adaptive modulation OLT 5 with respect to the downlink continuous signal received from the PAM adaptive modulation OLT 5. One of the multi-level PAM modulation and the binary OOK modulation larger than the binary value, the multi-level value of which is determined according to the transmission distance to the PAM adaptive modulation OLT 5 for the upstream burst signal transmitted to the PAM adaptive modulation OLT 5 Do.

  Here, each ONU 6 is determined according to the transmission distance from the PAM adaptive modulation OLT 5 to the downlink continuous signal received from the PAM adaptive modulation OLT 5 when performing PAM demodulation or OOK demodulation. Demodulate with multiple values. When each ONU 6 performs PAM modulation or OOK modulation, the ONU 6 is determined according to the transmission distance to the PAM adaptive modulation OLT 5 with respect to the upstream burst signal transmitted to the PAM adaptive modulation OLT 5 and does not degrade the signal-to-noise ratio. Modulation having a multilevel degree is performed.

  The transmission distance between the PAM adaptive modulation OLT 5 and each ONU 6 is estimated by the PAM adaptive modulation OLT 5 based on the ranging information when the PAM adaptive modulation OLT 5 performs dynamic band allocation to each ONU 6. Therefore, the transmission distance can be easily estimated.

  The formats of the upstream burst signal and downstream continuous signal according to the second embodiment are shown in FIGS. 11 and 12, only the ONUs 6-1m, 6-2m, and 6-nm are shown. The ONU 6-1-m is in an area where the PAM 8 signal can be applied, and the maximum multi-level is adopted among the allowable multi-levels. The upstream burst signal and the downstream continuous signal have the light intensity of “0”, “ This is a PAM8 signal modulated in eight stages of “1”, “2”, “3”, “4”, “5”, “6”, “7”. ONU6-n-m is in an area where the PAM4 signal can be applied, and the maximum multi-level is adopted among the allowable multi-levels. The upstream burst signal and the downstream continuous signal have the light intensity of “0”, “ This is a PAM4 signal modulated in four stages of “1”, “2”, and “3”. The ONU 6-2-m is in an area where the NRZ signal can be applied, and the maximum multi-level is adopted among the allowable multi-levels. The upstream burst signal and the downstream continuous signal have the light intensity of “0”, “ This is an NRZ signal modulated in two stages of 1 ″.

  FIG. 13 shows the configuration of the PAM adaptive modulation OLT according to the second embodiment. The PAM adaptive modulation OLT 5 includes a multi-level / binary modulation unit 51 and a multi-level / binary demodulation unit 52.

  The multi-level / binary modulation unit 51 synthesizes the outputs of two or three OOKs, thereby multi-levels (in this case, 4-level and 8-level) greater than 2-level for the downstream continuous signal transmitted to each ONU 6. ), And synthesizing outputs by synchronizing on / off of the three OOKs in the same state, thereby performing binary OOK modulation on the downstream continuous signal transmitted to each ONU 6. The multi-level / binary demodulator 52 performs multi-level (four-level and 8-level) PAM demodulation on the upstream burst signal received from each ONU 6 and upstream bursts received from each ONU 6. Perform binary OOK demodulation on the signal.

  The multi-level / binary modulation unit 51 includes electrical signal generation units 511, 512, and 513, a signal generation unit control unit 514, an electrical signal synthesis unit 515, and an optical signal generation unit 516. The second embodiment shown in FIG. The PAM4 signal, the PAM8 signal, and the NRZ signal are generated according to the generation method of the downstream continuous signal.

  The electrical signal generator 511 generates an electrical signal of “0” level or “1” level. The electric signal generator 512 generates an electric signal of “0” level or “2” level. The electric signal generation unit 513 generates an electric signal of “0” level or “4” level. The signal generation unit control unit 514 controls the electric signal generation units 511, 512, and 513 to generate which one of the electric signals that can be generated.

  The electrical signal synthesis unit 515 receives one of the electrical signals that can be generated from each of the electrical signal generation units 511, 512, and 513, and synthesizes the input electrical signals. The optical signal generator 516 receives the synthesized electrical signal from the electrical signal synthesizer 515, and directly modulates the laser itself or externally modulates the continuous optical signal based on the inputted synthesized electrical signal. , PAM4 signal, PAM8 signal and NRZ signal are generated.

  FIG. 15 shows the configuration of the ONU according to the second embodiment. The ONU 6 includes a multilevel modulation unit 61 and a multilevel demodulation unit 62. The multi-level modulation unit 61 synthesizes the outputs of two or three OOK, thereby multi-level (in this case, 4-level or 8-level) greater than 2 for the upstream burst signal transmitted to the PAM adaptive modulation OLT 5 PAM modulation is performed. The multi-level demodulator 62 performs multi-level (four-level or eight-level) PAM demodulation on binary continuous signals received from the PAM adaptive modulation OLT 5 in this case.

  The multi-level modulation unit 61 includes electric signal generation units 611, 612, and 613, a signal generation unit control unit 614, an electric signal synthesis unit 615, and an optical signal generation unit 616. Similar to the signal generation method, the PAM4 signal or the PAM8 signal is generated.

  In the second embodiment, since an OOK modulation method and a multi-value PAM method larger than two values are used, a higher speed and a larger capacity can be achieved than a simple OOK modulation method, and an OFDM technique and a digital coherent technique can be achieved. Therefore, it is possible to achieve economy, and thus it is possible to realize economical high speed and large capacity and flexible adaptive modulation.

  In the second embodiment, since the multi-value PAM system larger than the binary value is used based on the existing OOK modulation system, an existing optical device or electronic circuit can be applied. Therefore, economical high speed and large capacity can be achieved. And flexible adaptive modulation can be realized.

  Furthermore, in the second embodiment, the PAM signal or the OOK signal can be transmitted / received with the maximum multi-level that is determined according to the transmission distance and does not deteriorate the signal-to-noise ratio.

  Here, in the second embodiment, a multi-value PAM scheme that is larger than binary is used for both the upstream burst signal and the downstream continuous signal. On the other hand, as a modification, a multi-value PAM scheme larger than binary may be used for one of the upstream burst signal and the downstream continuous signal.

In the second embodiment, a 4-value and 8-value PAM method is used. On the other hand, as a modified example, a multi-value PAM method larger than 4-value and 8-value may be used. Here, when the ^2n- value PAM method is used, an electric signal generation unit that generates an electric signal of “0” level or “1” level, and an electric signal that generates an electric signal of “0” level or “2” level. A signal generator,..., An electric signal generator that generates an electric signal of “0” level or “2 ⁿ⁻¹ ” level may be arranged.

  Furthermore, in the second embodiment, a TDM-PON is configured using an optical splitter. On the other hand, as a modification, WDM-PON or TDM / WDM-PON may be configured by using AWG (Arrayed Waveguide Grating).

(Embodiment 3)
In the first embodiment, a modulation having a maximum multilevel value that is determined according to the transmission distance and does not deteriorate the signal-to-noise ratio is selected from among the PAM4 modulation and the PAM8 modulation. In the third embodiment, a modulation having a multilevel value determined according to a transmission distance and a communication band is selected from among PAM4 modulation and PAM8 modulation. FIG. 16 shows the configuration of the optical access system according to the third embodiment.

  The optical access system according to the third embodiment is a PON using the PAM method and adaptive modulation technology, and includes a PAM adaptive modulation OLT 7 installed in a communication carrier building, an ONU 8-1-1 installed in a user's house,. , 8--1-m, 8-2-1,..., 8--2-m,..., 8-n-1,. It is composed of an optical splitter and an optical fiber as a transmission path.

  In FIG. 16, the PAM adaptive modulation OLT 7 has a short distance from the PAM adaptive modulation OLT 7 in the ONUs 8-1-1,..., 8-1-1, 8-n-1,. And it is determined that it is in an area where the PAM8 signal can be applied. In addition, the PAM adaptive modulation OLT 7 has ONUs 8-2-1,..., 8-2-m at a long distance from the PAM adaptive modulation OLT 7 and is in an area where the PAM 8 signal cannot be applied and the PAM 4 signal can be applied. Judge that.

  The PAM adaptive modulation OLT 7 is a multi-level PAM modulation whose multi-level is determined in accordance with a transmission distance to each ONU 8 with respect to a downstream continuous signal transmitted to each ONU 8, and an upstream burst signal received from each ONU 8. On the other hand, multi-value PAM demodulation having a multi-value greater than two values, in which the multi-value degree is determined according to the transmission distance from each ONU 8, is performed.

  Here, the PAM adaptive modulation OLT 7 is a modulation having a multi-value degree determined according to the transmission distance to each ONU 8 and the communication band to each ONU 8 for the downstream continuous signal transmitted to each ONU 8 when performing PAM modulation. I do. Then, when performing PAM demodulation, the PAM adaptive modulation OLT 7 performs demodulation having multilevel values determined according to the transmission distance from each ONU 8 and the communication band from each ONU 8 with respect to the upstream burst signal received from each ONU 8. .

  Each ONU 8 transmits, to the PAM adaptive modulation OLT 7, a multi-value PAM demodulator having a multi-value degree larger than a binary value, which is determined according to the transmission distance from the PAM adaptive modulation OLT 7, with respect to the downlink continuous signal received from the PAM adaptive modulation OLT 7. The multi-level PAM modulation is performed with respect to the upstream burst signal to be larger than the binary value in which the multi-level is determined according to the transmission distance to the PAM adaptive modulation OLT 7.

  Here, when each ONU 8 performs PAM demodulation, the multilevel degree determined according to the transmission distance from the PAM adaptive modulation OLT 7 and the communication band from the PAM adaptive modulation OLT 7 for the downlink continuous signal received from the PAM adaptive modulation OLT 7. Is demodulated. When each ONU 8 performs PAM modulation, the multilevel degree determined according to the transmission distance to the PAM adaptive modulation OLT 7 and the communication band to the PAM adaptive modulation OLT 7 with respect to the upstream burst signal transmitted to the PAM adaptive modulation OLT 7 Modulation is performed.

  Since ONU8-1-m is in an area to which the PAM8 signal can be applied and the communication band is large, PAM8 modulation is selected as the maximum multi-level among the allowable multi-levels. The ONUs 8-1-1 and 8-n-1 are in the area where the PAM8 signal can be applied, but the communication band is medium. Modulation is selected. ONU8-nm is in an area where the PAM8 signal can be applied, but since the communication band is small, OOK modulation is selected as the minimum multilevel value among the allowable multilevel values.

  Since ONU8-2-1 is in an area to which a PAM4 signal can be applied and the communication band is large, PAM4 modulation is selected as the maximum multilevel value among the allowable multilevel values. The ONU8-2-m is in an area where the PAM4 signal can be applied, but since the communication band is small, the OOK modulation is selected as the minimum multilevel value among the allowable multilevel values.

  In the third embodiment, since a multi-value PAM method larger than binary is used without using an OOK modulation method, a higher speed and a larger capacity can be achieved than a simple OOK modulation method, and an OFDM technique or a digital coherent technique can be achieved. Thus, the economy can be improved, and therefore, economical high speed and large capacity and flexible adaptive modulation can be realized.

  In the third embodiment, since the multi-value PAM system larger than the binary value is used based on the existing OOK modulation system, an existing optical device or electronic circuit can be applied. And flexible adaptive modulation can be realized.

  Furthermore, in the third embodiment, a PAM signal or an OOK signal can be transmitted / received with a multi-value level determined according to both the transmission distance and the communication band.

(Embodiment 4)
In the second embodiment, a modulation having a maximum multilevel value that is determined according to a transmission distance and does not deteriorate a signal-to-noise ratio is selected from among PAM4 modulation, PAM8 modulation, and OOK modulation. In the fourth embodiment, a modulation having a multilevel value determined according to a transmission distance and a communication band is selected from among PAM4 modulation, PAM8 modulation, and OOK modulation. The configuration of the optical access system of the fourth embodiment is shown in FIG.

  The optical access system according to the fourth embodiment is a PON that uses a PAM system, an OOK modulation system, and an adaptive modulation technique, and includes a PAM adaptive modulation OLT 9 installed in a telecommunications carrier building and an ONU 10-1-1 installed in a user's home. ,..., 10-1-m, 10-2-1,... 10-2-m,..., 10-n-1,. It comprises an optical splitter that multiplexes and demultiplexes and an optical fiber that is a transmission path.

  In FIG. 17, the PAM adaptive modulation OLT 9 determines that the ONUs 10-1-1,..., 10-1 -m are in a short distance from the PAM adaptive modulation OLT 9 and are in an area where the PAM 8 signal can be applied. . In addition, the PAM adaptive modulation OLT 9 has ONUs 10-n-1,..., 10-nm in the middle distance from the PAM adaptive modulation OLT 9, and is in an area where the PAM 8 signal cannot be applied and the PAM 4 signal can be applied. Judge that. Further, the PAM adaptive modulation OLT 9 has ONUs 10-2-1,..., 10-2-m at a long distance from the PAM adaptive modulation OLT 9, and cannot apply the PAM8 signal and the PAM4 signal and can apply the NRZ signal. Judged to be in the area.

  The PAM adaptive modulation OLT 9 is one of a multi-value PAM modulation and a binary OOK modulation larger than a binary value whose multi-value degree is determined according to a transmission distance to each ONU 10 for a downstream continuous signal transmitted to each ONU 10. For the upstream burst signal received from each ONU 10, either multi-value PAM demodulation larger than binary or binary OOK demodulation whose multi-value is determined according to the transmission distance from each ONU 10 is performed.

  Here, the PAM adaptive modulation OLT 9 is a modulation having a multilevel value determined according to the transmission distance to each ONU 10 and the communication band to each ONU 10 for the downstream continuous signal transmitted to each ONU 10 when performing PAM modulation. I do. Then, when performing PAM demodulation, the PAM adaptive modulation OLT 9 demodulates the upstream burst signal received from each ONU 10 with multilevel values determined according to the transmission distance from each ONU 10 and the communication band from each ONU 10. .

  Each ONU 10 has either a multi-value PAM demodulation or a binary OOK demodulation larger than a binary value, the multi-value degree of which is determined according to the transmission distance from the PAM adaptive modulation OLT 9 for the downlink continuous signal received from the PAM adaptive modulation OLT 9. One of the multi-level PAM modulation and the binary OOK modulation larger than the binary value, the multi-level value of which is determined according to the transmission distance to the PAM adaptive modulation OLT 9 for the upstream burst signal transmitted to the PAM adaptive modulation OLT 9; Do.

  Here, each ONU 10, when performing PAM demodulation, has a multilevel value determined according to the transmission distance from the PAM adaptive modulation OLT 9 and the communication band from the PAM adaptive modulation OLT 9 for the downlink continuous signal received from the PAM adaptive modulation OLT 9. Is demodulated. When each ONU 10 performs PAM modulation, the multilevel degree determined in accordance with the transmission distance to the PAM adaptive modulation OLT 9 and the communication band to the PAM adaptive modulation OLT 9 with respect to the upstream burst signal transmitted to the PAM adaptive modulation OLT 9 Modulation is performed.

  Since the ONU 10-1-m is in an area where the PAM8 signal can be applied and the communication band is large, the PAM8 modulation is selected as the maximum multilevel value among the allowable multilevel values. The ONU 10-1-1 is in an area to which the PAM8 signal can be applied, but since the communication band is small, the PAM4 modulation is selected as an intermediate multilevel value among the allowable multilevel values.

  Since ONU10-n-1 is in an area to which a PAM4 signal can be applied and the communication band is large, PAM4 modulation is selected as the maximum multilevel degree among the allowable multilevel levels. The ONU 10-nm is in an area where the PAM4 signal can be applied, but since the communication band is small, the OOK modulation is selected as the minimum multi-level value among the allowable multi-level values.

  ONUs 10-2-1 to 10-2-m are in an area where an NRZ signal can be applied, and OOK modulation is selected regardless of the size of the communication band.

  In the fourth embodiment, since an OOK modulation method and a multi-value PAM method larger than two values are used, a higher speed and a larger capacity can be achieved than a simple OOK modulation method, and the OFDM technology and the digital coherent technology can be achieved. Therefore, it is possible to achieve economy, and thus it is possible to realize economical high speed and large capacity and flexible adaptive modulation.

  In the fourth embodiment, since the multi-value PAM system larger than the binary value is used based on the existing OOK modulation system, the existing optical device or electronic circuit can be applied. And flexible adaptive modulation can be realized.

  Furthermore, in the fourth embodiment, a PAM signal or an OOK signal can be transmitted / received at a multi-value level determined according to both the transmission distance and the communication band.

  The optical access system, the terminating device, the in-home device, and the optical access method of the present invention realize economical high speed, large capacity, and flexible adaptive modulation in a time division multiplexing optical access system and / or wavelength multiplexing optical access system. be able to.

1: QAM adaptive modulation OLT
2-1-1, 2-1-1m, 2-2-1, 2-2-2m, 2-n-1, 2-nm: ONU
3: PAM adaptive modulation OLT
4, 4-1-1, 4-1-m, 4-2-1, 4-2-2m, 4-n-1, 4-nm: ONU
5: PAM adaptive modulation OLT
6, 6-1-1, 6-1-m, 6-2-1, 6-2m, 6-n-1, 6-nm: ONU
7: PAM adaptive modulation OLT
8-1-1, 8-1-1, 8-2-1, 8--2-m, 8-n-1, 8-nm: ONU
9: PAM adaptive modulation OLT
10-1-1, 10-1-m, 10-2-1, 10-2-m, 10-n-1, 10-nm: ONU
31: Multi-level modulation unit 32: Multi-level demodulation unit 41: Multi-level modulation unit 42: Multi-level demodulation unit 51: Multi-level / binary modulation unit 52: Multi-level / binary demodulation unit 61: Multi-level modulation unit 62: Multilevel demodulator 311, 312, 313: electrical signal generator 314: signal generator controller 315: electrical signal synthesizer 316: optical signal generator 411, 412, 413: electrical signal generator 414: signal generator controller 415: Electric signal synthesizer 416: Optical signal generators 511, 512, 513: Electric signal generator 514: Signal generator controller 515: Electric signal synthesizer 516: Optical signal generators 611, 612, 613: Electric signal generator Unit 614: Signal generation unit control unit 615: Electric signal synthesis unit 616: Optical signal generation unit

Claims (8)

An optical access system comprising a termination device and a plurality of in-home devices,
The terminating device has a multi-value pulse intensity modulation greater than a binary value that has a multi-value degree determined according to a transmission distance to the in-home device for a downlink signal transmitted to the in-home device, and an uplink received from the in-home device. Performing one or both of multi-level pulse intensity demodulation greater than binary and multi-level determined according to the transmission distance from the in-home device for the signal,
The in-home device is configured to demodulate a multi-level pulse intensity demodulated with a multi-level value that is determined according to a transmission distance from the end device with respect to a downlink signal received from the end device, and to transmit to the end device. An optical access system characterized in that one or both of multi-level pulse intensity modulation with a multi-level value larger than 2 is determined according to a transmission distance to the terminal device for a signal. An optical access system comprising a termination device and a plurality of in-home devices,
The terminating device has either a multi-value pulse intensity modulation greater than a binary value or a binary on-off modulation with a multi-value degree determined according to a transmission distance to the home device for a downlink signal transmitted to the home device. One of the multi-level pulse intensity demodulation and the binary on-off demodulation larger than binary, the multi-level of which is determined according to the transmission distance from the in-house device, with respect to the uplink signal received from the in-home device, or Do both
The in-home device has one of multi-level pulse intensity demodulation and binary on-off demodulation larger than binary, the multi-level of which is determined according to the transmission distance from the termination device with respect to the downlink signal received from the termination device. One of the multi-level pulse intensity modulation and the binary on-off modulation larger than binary, the multi-level of which is determined according to the transmission distance to the termination device, with respect to the uplink signal transmitted to the termination device, or An optical access system characterized by performing both. The terminating device receives from the in-house device a modulation having a maximum multi-level that is determined in accordance with a transmission distance to the in-home device with respect to a downlink signal transmitted to the in-home device and does not deteriorate a signal-to-noise ratio. Performing one or both of the demodulation and the maximum multi-level that does not degrade the signal-to-noise ratio determined according to the transmission distance from the in-home device for the upstream signal,
The in-home device determines the maximum downlink value that is determined according to the transmission distance from the terminal device and does not deteriorate the signal-to-noise ratio with respect to the downlink signal received from the terminal device, and transmits the demodulated signal to the terminal device 3. The method according to claim 1, wherein one or both of an uplink signal and a modulation having a maximum multi-level that does not deteriorate a signal-to-noise ratio that is determined according to a transmission distance to the terminating device are performed. The optical access system described. The terminating device has a modulation having a multilevel value determined according to a transmission distance to the in-home device and a communication band to the in-home device for a downlink signal transmitted to the in-home device, and an uplink received from the in-home device. Performing one or both of a signal, a demodulation having a multivalued degree determined according to a transmission distance from the in-home device and a communication band from the in-home device,
The in-home device demodulates the downlink signal received from the termination device, has a multilevel value determined according to the transmission distance from the termination device and the communication band from the termination device, and transmits to the termination device 3. The modulation according to claim 1, wherein one or both of a modulation having a multi-level value determined according to a transmission distance to the termination device and a communication band to the termination device is performed on a signal. Optical access system. The transmission distance between the terminating device and the in-home device is estimated by the terminating device based on ranging information when the terminating device performs dynamic bandwidth allocation to the in-home device. 5. The optical access system according to any one of items 1 to 4. An end device that communicates with a home device in an optical access system,
A multi-level modulation unit that performs multi-level pulse intensity modulation greater than a binary value that has a multi-value degree determined according to a transmission distance to the home device with respect to a downlink signal transmitted to the home device, and received from the home device A multi-level demodulating unit that performs multi-level pulse intensity demodulation with a multi-level greater than a binary value, the multi-level of which is determined according to the transmission distance from the in-house device for an upstream signal, and one or both of them. apparatus. A home device that communicates with a terminating device in an optical access system,
A multi-level demodulating unit that performs multi-level pulse intensity demodulation with a multi-level greater than a binary value that is determined according to a transmission distance from the terminal device with respect to a downlink signal received from the terminal device, and transmits the signal to the terminal device One or both of a multi-level modulation unit that performs multi-level pulse intensity modulation with a multi-level value larger than a binary value that has a multi-level value determined according to a transmission distance to the terminal device for an upstream signal. apparatus. An optical access method using an end device and a plurality of in-home devices,
The terminating device performs multi-level pulse intensity modulation, which is greater than two values whose multi-level is determined according to a transmission distance to the in-home device, with respect to a downlink signal transmitted to the in-home device, Downlink signal modulation / demodulation step for performing multi-level pulse intensity demodulation greater than binary with a multi-level degree determined according to the transmission distance from the end device with respect to the down signal received from the end device;
The in-home device performs multi-value pulse intensity modulation larger than two values, the multi-value degree of which is determined according to the transmission distance to the end device, for the uplink signal transmitted to the end device, An uplink signal modulation / demodulation step for performing multi-level pulse intensity demodulation greater than binary, the multi-level being determined according to the transmission distance from the in-home device, with respect to the up-link signal received from the in-home device;
An optical access method characterized by performing one or both of the following:

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