KR102024433B1 - Optical line terminal and optical network unit and optical communication system using the same - Google Patents

Abstract

Disclosed are an optical line terminal, an optical termination device, and an optical communication system including the same. An optical communication system according to an embodiment of the present invention generates an RF clipping tone, pulses the RF clipping tone, modulates seed light with the pulse patterned RF clipping tone, and generates an optical carrier signal. An optical line terminal transmitting a carrier signal to a plurality of optical termination devices, receiving uplink signals from the plurality of optical termination devices, receiving an optical carrier signal from the optical line terminal, and modulating the optical carrier signal into an uplink signal And a plurality of optical termination devices that time-adjust the uplink signal and transmit the time-adjusted uplink signal to an optical line terminal.

Description

 Optical line terminal, optical termination unit, and optical communication system including the same {OPTICAL LINE TERMINAL AND OPTICAL NETWORK UNIT AND OPTICAL COMMUNICATION SYSTEM USING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical communications, and more particularly, to reducing optical beat interference (OBI) and increasing the number of optical network units (ONUs) through pulse patterning. The present invention relates to an optical communication system.

Traffic is continuously increasing in subscriber networks, requiring efficient transmission techniques within limited bandwidth. Orthogonal Frequency Division Multiplexing (OFDM) is used as a standard in wireless subscriber networks as a method for increasing bandwidth efficiency.

In the optical subscriber network, wavelength division multiplexing (WDM) based systems are standardized. In order to improve the efficiency of the entire WDM system, it is required to increase the efficiency per wavelength and increase the number of multiple accesses within a single wavelength.

1 is a diagram illustrating uplink multiple access in a passive optical network (PON) based on WDM-OFDM according to the prior art.

Referring to FIG. 1, light in a laser is not a perfect monochromatic light, but is randomly generated with a line width around a reference wavelength.

Light sources generated in different optical network units (ONUs) have different phases and frequencies by using a random photon emission process, even when using lasers having the same center wavelength.

)로 검출이 되며 하기 수학식 1로 표현된다.Therefore, in uplink transmission of multiple accesses sharing the same center wavelength channel, different light sources transmitted from each ONU (ONU1, ONU2, ONU3) are simultaneously received by the optical line terminal (OLT). The signals transmitted optically from several ONUs (ONU1, ONU2, ONU3) are converted into photocurrents by square-law detection at the photodiode (PD) of the optical line terminal.

) Is detected by Equation 1 below.

[Equation 1]

는 위상을, k와 n은 서로 다른 광캐리어를 나타낸다. Where R is the receiver sensitivity, E is the light field, I is the intensity of light current, v is the frequency of light,

Denotes a phase, and k and n denote different optical carriers.

The last term in Equation 1 represents the light beating component.

The optical beating component is generated by using a wavelength difference between optical carriers as a center frequency, and appears in the form of a convolution of a power spectral density (PSD) of each optical field.

Therefore, in the case of uplink multiplexing within a single wavelength in a PON system using a laser diode (LD) as a light source, an optical beating interference noise of a Lorentz function centering on a low frequency band is provided. Beat Interference (OBI) 150 occurs.

OBI may cause a problem that it is impossible to detect an uplink multiple access signal in a frequency multiplexing system within a single wavelength such as OFDM (or subcarrier multiplexing (SCM)). Even in the case of a source seeding system that injects the same light source, the light source reflected from the ONU has different characteristics.

Therefore, in the source seeding system, OBI occurs as in the case of using an independent light source, which makes it difficult to detect an uplink transmitted signal.

Techniques for reducing OBI include: (1) carrier suppression & coherent detection, (2) wavelength separation, (3) orthogonal dual polarization, (4) Spectrum broadening has been proposed. These techniques have high complexity, limited scalability for WDM systems, or limited scalability to polarization division multiplexing (PDM).

Republic of Korea Patent Publication No. 10-0621217 (August 30, 2006) "Optical receiver for reducing optical interference noise and optical communication network having the same"

An optical line terminal, an optical termination device, and an optical communication system including the same to alleviate optical beat interference (OBI) using RF clipping tones.

In addition, the present invention provides an optical communication terminal including an optical line terminal, an optical termination device having a wide optical delay dynamic range (ODDR) by pulse patterning an RF clipping tone, and an optical communication system including the same.

In addition, the present invention provides an optical line terminal, an optical termination device, and an optical communication system including the same, by suppressing optical beating interference noise by pulse patterning an RF clipping tone and increasing the number of connectors of an ONU.

Another object of the present invention is to provide an optical line terminal, an optical termination device, and an optical communication system including the same, so as to satisfy the time regularity (orthogonality) of the RF clipping tone to reduce optical beat interference (OBI).

 According to an embodiment of the present invention, an optical line terminal generates an RF clipping tone, and a patterning unit for pulse patterning the RF clipping tone, and modulating seed light with the pulse patterned RF clipping tone. And an optical carrier generator for generating an optical carrier signal, a transmitter for transmitting the optical carrier signal to a plurality of optical termination devices, and a receiver for receiving uplink signals from the plurality of optical termination devices.

The patterning unit may pulse pattern the RF clipping tone based on the number of the plurality of optical termination devices, increase the number of optical termination devices satisfying orthogonality between the uplink signals, and reduce optical beating interference noise.

The optical carrier generator may modulate the seed light into the pulse patterned RF clipping tone to expand the spectrum of the seed light and reduce optical beating interference noise.

An optical termination device according to an embodiment of the present invention includes a receiver for receiving an optical carrier signal to which pulse patterning is applied from an optical line terminal, a modulator for modulating the optical carrier signal into an uplink signal, and a time adjustment for the uplink signal. And a delay line unit and a transmitter for transmitting the time-adjusted uplink signal to the optical line terminal.

The delay line unit may reduce optical beating interference noise by adjusting time to satisfy orthogonality between uplink signals from a plurality of optical termination devices.

An optical communication system according to an embodiment of the present invention generates an RF clipping tone, pulses the RF clipping tone, modulates seed light with the pulse patterned RF clipping tone, and generates an optical carrier signal. An optical line terminal transmitting a carrier signal to a plurality of optical termination devices, receiving uplink signals from the plurality of optical termination devices, receiving an optical carrier signal from the optical line terminal, and modulating the optical carrier signal into an uplink signal And a plurality of optical termination devices that time-adjust the uplink signal and transmit the time-adjusted uplink signal to an optical line terminal.

An optical line terminal, an optical termination device, and an optical communication system including the same may reduce optical beat interference (OBI) by using an RF clipping tone.

In addition, the optical line terminal, the optical termination device and the optical communication system including the same according to an embodiment of the present invention can widen the optical delay dynamic range (ODDR) by pulse patterning the RF clipping tone. have.

In addition, the optical line terminal, the optical termination device and the optical communication system including the same according to an embodiment of the present invention can increase the number of users of the ONU by pulse patterning the RF clipping tone.

In addition, the optical line terminal, the optical termination device and the optical communication system including the same according to an embodiment of the present invention to satisfy the time regularity (orthogonality) of the RF clipping tone to reduce the optical beat interference (OBI) I can alleviate it.

1 is a diagram illustrating uplink multiple access in a passive optical network (PON) based on WDM-OFDM according to the prior art.
2 is a block diagram of an optical line terminal according to an embodiment of the present invention.
3 is a block diagram of an optical termination device according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating signals transmitted between an optical line terminal (OLT) and an optical network unit (ONU) constituting an optical communication system according to an embodiment of the present invention.
5 is a view for explaining an optical communication system according to an embodiment of the present invention.
6 is a graph showing channel performance results in an optical communication system according to an embodiment of the present invention.
FIG. 7 is a diagram illustrating bandwidth efficiency and bit-loading profile and constellation at 350ps according to optical delay.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings and the contents described in the accompanying drawings, but the present invention is not limited or limited to the embodiments.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, “comprises” and / or “comprising” refers to the presence of one or more other components, steps, operations and / or elements. Or does not exclude additions.

As used herein, “an embodiment”, “an example”, “side”, “an example”, etc., should be construed that any aspect or design described is better or advantageous than other aspects or designs. It is not.

In addition, the term 'or' means inclusive or 'inclusive or' rather than 'exclusive or'. In other words, unless stated otherwise or unclear from the context, the expression 'x uses a or b' means any one of natural inclusive permutations.

Also, the singular forms “a” or “an”, as used in this specification and in the claims, generally refer to “one or more” unless the context clearly dictates otherwise or in reference to a singular form. Should be interpreted as

In addition, terms such as first and second used in the present specification and claims may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used in a sense that can be commonly understood by those skilled in the art. In addition, the terms defined in the commonly used dictionaries are not ideally or excessively interpreted unless they are specifically defined clearly.

On the other hand, in describing the present invention, when it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. Terminology used herein is a term used to properly express an embodiment of the present invention, which may vary according to a user, an operator's intention, or a custom in the field to which the present invention belongs. Therefore, the definitions of the terms should be made based on the contents throughout the specification.

2 is a block diagram of an optical line terminal according to an embodiment of the present invention.

In FIGS. 2-3 and 5-7 the term orthogonality means orthogonality or near-orthogonality.

Referring to FIG. 2, the optical line terminal 200 includes a patterning unit 210, an optical carrier generating unit 220, a transmitter 230, and a receiver 240.

The patterning unit 210 generates a radio frequency (RF) clipping tone.

The patterning unit 210 pulses the RF clipping tone.

The patterning unit 210 may adjust the duty cycle of the RF clipping tone by performing pulse patterning.

The patterning unit 210 may pulse pattern the RF clipping tone to satisfy orthogonality (time regularity) between uplink signals of the plurality of optical termination devices. This increases the number of optical termination devices and reduces optical beating interference noise.

For example, if the number of ONUs is three, the RF clipping tone can be patterned with [1,0,0] to satisfy orthogonality between upstream signals from the ONUs.

Alternatively, when the number of ONUs is 5, the RF clipping tone may be patterned to [1,0,0,0,0] to satisfy orthogonality between uplink signals from the ONUs.

That is, OBI can be lowered by performing pulse patterning according to the number of ONUs.

The patterning unit 210 transmits the pulse patterned RF clipping tone to the optical carrier generator 220.

The optical carrier generating unit 220 generates seed light.

A distributed-feedback laser diode (DFB-LD) may be used to generate seed light.

The optical carrier generator 220 modulates the generated seed light into a pulse patterned RF clipping tone to generate an optical carrier signal.

The optical carrier signal has the effect of broadening the spectrum by pulse patterned RF clipping tones. Moderate linewidth extension within a single wavelength channel reduces OBI by allowing the OBI to spread flat over a broad spectrum.

The transmitter 230 transmits the optical carrier signal to the plurality of optical termination devices.

A reflective semiconductor optical amplifier (RSOA) of an optical termination device generates an uplink signal by modulating an Orthogonal Frequency Division Multiplexing (OFDM) signal including data with a transmitted optical carrier signal.

The receiver 240 receives upward signals from the plurality of optical termination devices.

The receiver 240 receives the uplink signals combined in the optical distribution network (ODN).

The combined uplink signals satisfy orthogonality (time regularity) between the uplink signals by time adjustment of the optical termination devices.

Therefore, OBI can be significantly reduced when the optical line terminal receives the combined uplink signals.

In FIG. 2, the optical line terminal generates an RF clipping tone, generates a patterning unit for pulse patterning the RF clipping tone, generates seed light, and modulates the generated seed light directly into a pulse patterned RF clipping tone to generate an optical carrier signal. The optical carrier generation unit to generate and the transmission unit for transmitting the optical carrier signal to the plurality of optical termination devices, but the configuration may be located in the vicinity (remote node, Remote Node) of the optical termination devices.

Thus, it is also possible to generate an optical carrier in the vicinity of the optical termination devices and to transmit a pulse patterned optical carrier signal to the optical termination devices.

3 is a block diagram of an optical termination device according to an embodiment of the present invention.

Referring to FIG. 3, the optical termination device 300 includes a receiver 310, a modulator 320, a delay line unit 330, and a transmitter 340.

The receiver 310 receives the optical carrier signal from the optical line terminal.

The modulator 320 generates an uplink signal by modulating an Orthogonal Frequency Division Multiplexing (OFDM) signal into an optical carrier signal.

For example, the modulator 320 may use a reflective semiconductor optical amplifier (RSOA).

The delay line unit 330 time adjusts the up signal.

The delay line unit 330 time adjusts the uplink signal to satisfy the time regularity (orthogonality) between the plurality of optical termination devices.

That is, the time is adjusted so that the maximum value peak of an uplink signal of any particular optical termination device and the minimum values of uplink signals of other optical termination devices can be optically coupled.

The time-adjusted uplink signal satisfies orthogonality with the uplink signals of other optical termination devices.

For example, when the RF clipping tone of the optical carrier signal is pulse patterned as [1,0,0], the delay line unit 330 may adjust the uplink signal in consideration of the patterning of the RF clipping tone.

The uplink signals satisfying the orthogonality are combined and received by the optical line terminal.

The optical line terminal may reduce the OBI upon receiving uplink signals satisfying orthogonality.

In FIG. 3, the optical termination device includes a delay line part 330 for adjusting time, but the delay line part may be located in the optical distribution network or may be located between the optical termination devices and the optical distribution network to time-control upstream signals. .

The transmitter 340 transmits the time-controlled uplink signal to the optical line terminal.

The time-adjusted uplink signals are combined in the optical distribution network, and the combined signal is received by the optical line terminal.

FIG. 4 is a diagram illustrating signals transmitted between an optical line terminal (OLT) and an optical network unit (ONU) constituting an optical communication system according to an embodiment of the present invention.

In FIG. 4, the optical communication system is composed of two optical termination units ONU, but may be composed of one or more optical termination units ONU.

Referring to FIG. 4, the OLT transmits an optical carrier signal to the ONU.

The optical carrier signal can be assumed to be an ideal square pulse train with a 50% duty cycle.

The optical carrier signals p ₁ (t) and p ₂ (t) may be represented by Equation 1 below.

[Equation 1]

Where T is a repetition period, p _n (t) is the ideal square pulse train delivered to the nth ONU, and d _1n is the optical delay between the first ONU and the nth ONU.

)을 제외하고, 동일한 신호이다.Since p ₁ (t) and p ₂ (t) are light pulse trains generated simultaneously before seeding, the optical delay (

Except), the same signal.

The ONUs modulate an OFDM signal with an optical carrier signal, generate an uplink signal, and transmit the uplink signal to the OLT.

The Xiangyang signal x ₁ (t), x ₂ (t) can be represented by the following equation (2).

[Equation 2]

Where s _n (t) is the OFDM signal of the nth ONU

The uplink signals are combined via an optical distribution network (ODN) and transmitted to the OLT.

Combined uplink signals should satisfy orthogonality (time regularity) between uplink signals to avoid inter-signal interference and maximize OBI reduction.

Orthogonality between the uplink signals x ₁ (t) and x ₂ (t) may be defined by Equation 3 below.

[Equation 3]

That is, if the upstream signals x ₁ (t) and x ₂ (t) are completely staggered, the orthogonality may be satisfied.

x ₁ (t) and x ₂ (t) are completely staggered when d ₁₂ = T / 2, thereby satisfying the orthogonality of Equation (3).

Thus, orthogonality can be satisfied by adjusting the optical delay between ONUs.

However, if the duty cycle is 50%, the orthogonality is very difficult to satisfy because the possible delay range is very narrow.

This range is referred to as Optical Delay Dynamic Range (ODDR).

ODDR can be defined as a possible delay range.

Uplink signals with a 50% duty cycle have zero ODDR, which guarantees complete orthogonality.

To extend the ODDR, the shape of the light pulse train can be modified.

This can be adjusted by pulse patterning the RF clipping tone.

Pulse patterning changes the duty cycle of the RF clipping tone.

If pulse patterning is used in a system consisting of two ONUs, the optical carrier signal (ideal square pulse sequence, p ₁ (t)) can be generalized as in Equation 4 below.

[Equation 4]

Where k (0 <k <0.5) is the duty cycle

In this case, p ₂ (t) may be represented by a signal delayed by d ₁₂ in p ₁ (t) of Equation 4.

일 때, 만족할 수 있다.Orthogonality of Equation 3

Can be satisfied.

이 되도록 확장될 수 있다.Where ODDR is

Can be extended to

일 때, 만족할 수 있다. 이때, ODDR은 50%까지 확장될 수 있다.If the duty cycle of the optical carrier signal is 25%, the orthogonality

Can be satisfied. At this time, the ODDR may be extended to 50%.

In addition to stabilizing orthogonal conditions, extended ODDR can increase the number of ONUs.

Accordingly, the pulse patterning based uplink signals may be generalized by Equation 5 below.

[Equation 5]

Where d ₁₁ is 0.

Orthogonality can also be generalized to Equation 6 below.

[Equation 6]

를 만족해야 한다.For example, in an optical communication system composed of three ONUs, in order to satisfy orthogonality,

Must be satisfied.

,

에 대한 해결책은 없다.But if the duty cycle is 50%,

,

There is no solution.

To solve this problem, pulse patterning can be used.

It has a reduced duty cycle based on the pattern of the RF clipping tone.

,

가

,

일 때 만족할 수 있다.For example, if the duty cycle is 1/3 (m = 3), the orthogonality between the three ONUs

,

end

,

Can be satisfied when

Thus, it is possible to increase the number of ONUs with orthogonality.

In addition, in an optical communication system consisting of two ONUs, when the duty cycle is 1/5 (m = 5), the ODDR is 60%.

This allows two ONUs to occupy 40% of the period of the light pulse train and the remaining 60% can be used to increase the number of ONUs. One ONU takes up 20% of the cycle. Up to five ONUs can be operated with orthogonality.

Accordingly, an optical communication system according to an embodiment of the present invention can support a plurality of ONUs according to a duty cycle of a single wavelength multiple access system without reduced OBI and interference between optical pulses.

The optical carrier signal (optical pulse train) may be non-ideal and not a rectangular pulse train because of the limited frequency response of the electrical device and the optical devices.

)은 pseudo 펄스 열이라 칭할 수 있으며, 하기 수학식 7로 표현될 수 있다.These pulse trains (

) May be referred to as a pseudo pulse train, and may be represented by Equation 7 below.

[Equation 7]

In this case, the limited frequency response may be considered as an effect of a low-pass filter (LPF).

Also, since the seed source is generated in the RF clipping tone, the pseudo pulse train is not perfectly on-off.

In this case, the term near-orthogonality may be more appropriate than orthogonality.

Near-orthogonality may be defined by Equation 8 below.

[Equation 8]

Conditions for satisfying near-orthogonality may be relaxed than orthogonality.

In this case, the condition of proximity orthogonality may be considered as a range for minimizing interference between uplink signals.

5 is a view for explaining an optical communication system according to an embodiment of the present invention.

Referring to FIG. 5, the optical communication system includes an optical line terminal 510 and optical termination devices ONU1, ONU2, ONU3, 530-1, 530-2, and 530-3.

In FIG. 5, three optical termination devices ONU1, ONU2, ONU3, 530-1, 530-2, and 530-3 may be configured. However, four or more optical termination devices may be used.

The optical line terminal 510 generates an RF clipping tone, pulses the RF clipping tone, and modulates the seed light with the pulse patterned RF clipping tone to generate the optical carrier signal 520.

The optical carrier signal 520 is sent to ONU1, ONU2 and ONU3.

In FIG. 5, an optical line terminal generates an RF clipping tone, pulses an RF clipping tone, generates seed light, and directly modulates the generated seed light into a pulse patterned RF clipping tone to generate and transmit an optical carrier signal. Transmit to terminators (ONU1, ONU2, ONU3, 530-1, 530-2, 530-3), but generate optical carrier signals and optical terminators (ONU1, ONU2, ONU3,530-1, 530-2, Transmission to 530-3 may be performed by a separate device located near (remote node) the optical termination devices ONU1, ONU2, ONU3, 530-1, 530-2, 530-3. .

The optical termination devices ONU1, ONU2, ONU3,530-1, 530-2, and 530-3 modulate the OFDM signals (electrical signals) 540-1,540-2,540-3 into the optical carrier signals 520 to upward. The signals 550-1, 550-2, 550-3 are generated, time adjusted to satisfy orthogonality with other ONUs, and transmitted upward to the optical line terminal 510.

The uplink signals 550-1, 550-2, 550-3 are combined in the optical distribution network 560 and transmitted to the optical line terminal 510.

In FIG. 5, the optical termination devices ONU1, ONU2, ONU3, 530-1, 530-2, and 530-3 perform time adjustment to satisfy orthogonality between uplink signals, but the time adjustment is performed by the optical distribution network 560. Alternatively, the operation may be performed through a separate device located between the optical termination devices ONU1, ONU2, ONU3, 530-1, 530-2, and 530-3 and the optical distribution network 560.

The optical line terminal 510 receives the combined uplink signals 570.

The photodiode of the optical line terminal 510 may receive with the OBI significantly reduced when receiving the combined uplink signals satisfying the orthogonality.

6 to 7 show an optical communication system including two optical terminators ONU1 and ONU2 having an optical path difference of 2.5 km, optical terminators ONU1 and ONU2 and an optical line terminal OLT having an optical path difference of 23 km. Experimental results at

The frequency of the RF clipping tone is 1.25 GHz, with a duty cycle of 0.5 (50%) (OPDM without pulse patterning) and 0.25 (25%) (e-OPDM with pulse patterning). Comparative experiment.

The optical delay generated from one ONU1 was optically delayed, and the result was observed.

6 is a graph showing channel performance results in an optical communication system according to an embodiment of the present invention.

Referring to FIG. 6, in FIG. 6, (a) is a case where pulse patterning is not used, and in FIG. 6 (b) is a duty by inserting a pattern of [1,0,0,0] when generating an RF clipping tone. This is the case when an optical carrier signal with a cycle of 25% is used.

In the upper graphs of FIG. 6, the horizontal axis represents an optical delay, the left vertical axis represents a subcarrier index, and the right vertical axis represents channel performance as an error vector magnitude (EVM). The lower graphs show the optical delay on the horizontal axis, and the vertical axis shows the average value (Average EVM) of the error vector magnitude of the subcarriers according to each optical delay.

In (a) and (b), since the RF clipping tone of 1.25 GHz is directly modulated, it can be confirmed that the orthogonality per 800 ps is satisfied.

At optical delays of around 150ps and 950ps, the EVM is the highest.

At 300ps (a) still has a high EVM, and (b) has a duty cycle of 0.25, which improves the EVM.

For example, the required EVM for 16-QAM is 12.5%.

This condition is satisfied at 500-550ps in (a), but extends to 300-650ps in (b).

As described with reference to FIG. 4, the duty cycle of 0.25 may be extended so that the ODDR becomes 50% in accordance with (b).

In one period of (b), it can be seen that from 150ps to 950ps, that is, 9 out of 17 intervals have good channel EVM with very low interference, and the other 8 have poor performance with relatively high interference.

Therefore, ODDR is almost 50%, and it can be confirmed that ODDR is experimentally expanded through pulse patterning.

That is, it can be seen that the pulse patterning has good channel performance in a much wider optical delay period.

FIG. 7 is a diagram illustrating bandwidth efficiency and bit-loading profile and constellation at 350ps according to optical delay.

Referring to FIG. 7, the left side of FIG. 7 shows the spectral efficiency (SE) of an uplink signal obtained by applying pulse patterning.

This shows SE in case of applying adaptive modulation to channel information of FIG. 6.

In good channel conditions, the SE increases because many bits can be transmitted.

OPDM and e-OPDM performing pulse patterning are the same at the peak value of SE.

That is, it can be seen that OBI reduction performance is similar.

However, there is a big difference in the section that can maintain a high SE. This means that there is a big difference in ODDR between e-OPDM and OPDM.

For example, a high SE of 0.25 duty cycle (e-OPDM) at 350ps optical delay, while a low SE of 0.5 duty cycle (OPDM).

7 shows the loading profile and constellation at 350 ps optical delay.

The right horizontal axis of FIG. 7 represents a subcarrier index, and the right vertical axis represents loaded bits.

In case of e-OPDM, bits 3 to 5 can be stored, but in case of OPDM, 1 or 0 bits can be loaded.

ODDR capable of SE over 3.5bit / s / Hz can be extended to 4.5x by halving the duty cycle through pulse patterning.

Accordingly, it can be seen that pulse patterning can alleviate the condition that satisfies the orthogonality and increase the number of ONUs with the extended ODDR.

In other words, by applying a shorter duty cycle through pulse patterning, the number of ONUs satisfying orthogonality can be increased.

The apparatus described above may be implemented as a hardware component, a software component, and / or a combination of hardware components and software components. For example, the devices and components described in the embodiments may be, for example, processors, controllers, arithmetic logic units (ALUs), digital signal processors, microcomputers, field programmable arrays (FPAs), It may be implemented using one or more general purpose or special purpose computers, such as a programmable logic unit (PLU), microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to the execution of the software. For convenience of explanation, one processing device may be described as being used, but one of ordinary skill in the art will appreciate that the processing device includes a plurality of processing elements and / or a plurality of types of processing elements. It can be seen that it may include. For example, the processing device may include a plurality of processors or one processor and one controller. In addition, other processing configurations are possible, such as parallel processors.

The software may include a computer program, code, instructions, or a combination of one or more of the above, and configure the processing device to operate as desired, or process it independently or collectively. You can command the device. Software and / or data may be any type of machine, component, physical device, virtual equipment, computer storage medium or device in order to be interpreted by or to provide instructions or data to the processing device. Or may be permanently or temporarily embodied in a signal wave to be transmitted. The software may be distributed over networked computer systems so that they may be stored or executed in a distributed manner. Software and data may be stored on one or more computer readable recording media.

The method according to the embodiment may be embodied in the form of program instructions that can be executed by various computer means and recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the media may be those specially designed and constructed for the purposes of the embodiments, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

Although the embodiments have been described by the limited embodiments and the drawings as described above, various modifications and variations are possible to those skilled in the art from the above description. For example, the described techniques may be performed in a different order than the described method, and / or components of the described systems, structures, devices, circuits, etc. may be combined or combined in a different form than the described method, or other components. Or even if replaced or substituted by equivalents, an appropriate result can be achieved.

Therefore, other implementations, other embodiments, and equivalents to the claims are within the scope of the claims that follow.

Claims (9)

A patterning unit configured to generate an RF clipping tone and pulse pattern the RF clipping tone;
An optical carrier generator for modulating seed light into the pulse patterned RF clipping tone to generate an optical carrier signal;
A transmitter for transmitting the optical carrier signal to a plurality of optical termination devices; And
It includes a receiver for receiving uplink signals from the plurality of optical termination device
Optical line terminal. The method of claim 1,
The patterning unit,
Pulse patterning the RF clipping tone based on the number of the plurality of optical termination devices, increasing the number of optical termination devices satisfying orthogonality between the uplink signals and reducing optical beating interference noise.
Optical line terminal. The method of claim 1,
The optical carrier generation unit,
Modulating the seed light with the pulse patterned RF clipping tone to broaden the spectrum of the seed light and to reduce optical beating interference noise
Optical line terminal. A receiver for receiving an optical carrier signal to which pulse patterning is applied from the optical line terminal;
A modulator for modulating the optical carrier signal into an uplink signal;
A delay line unit configured to time-control the uplink signal; And
And a transmitter for transmitting the time-adjusted uplink signal to the optical line terminal. The method of claim 4, wherein
The delay line unit,
Reduces optical beating interference by adjusting time to satisfy orthogonality between uplink signals from a plurality of optical termination devices
Optical termination device. Generate an RF clipping tone, pulse pattern the RF clipping tone, modulate a seed light with the pulse patterned RF clipping tone to generate an optical carrier signal, transmit the optical carrier signal to a plurality of optical termination devices, An optical line terminal for receiving uplink signals from the plurality of optical termination devices; And
A plurality of optical termination devices for receiving an optical carrier signal from the optical line terminal, modulating the optical carrier signal into an uplink signal, time-adjusting the uplink signal, and transmitting the time-adjusted uplink signal to the optical line terminal Containing
Optical communication system. The method of claim 6,
The optical line terminal,
Pulse patterning the RF clipping tone to increase the number of optical termination devices satisfying orthogonality between the upstream signals and to reduce optical beating interference noise.
Optical communication system. The method of claim 6,
The optical line terminal,
Modulate with the pulse patterned RF clipping tone to broaden the spectrum of the seed light and reduce optical beating interference
Optical communication system. The method of claim 6,
Each of the plurality of optical termination devices,
Reducing optical beating interference noise by adjusting time to satisfy orthogonality between uplink signals from the plurality of optical termination devices.
Optical communication system.

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