JP2016039526A - Optical amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical amplifier capable of amplifying two optical signals of different standards (dual rate), and capable of being extended.SOLUTION: Firstly, an optical amplifying device includes at least one demultiplexer capable of demultiplexing an input optical signal with a wavelength of n sections, where n is a natural number of 2 or more, n optical amplifiers capable of optically amplifying the optical signal subjected to wavelength separation for each wavelength section, and at least one multiplexer capable of multiplexing the optical signals amplified with respective wavelengths. Secondly, in order to remove SE noise superposed after optical amplification, the transparent band width of any or both of the demultiplexer and multiplexer has a window including adjoining wavelength sections at the time of wavelength separation and a constant overlapping section.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical amplifying apparatus for extending an optical access system.

  Due to the explosive increase in the amount of communication traffic in recent years, higher speed is required for an access network connecting an equipment center and a user. At the same time, there is also a need for high economic efficiency so as not to raise the service provision price compared to existing services. There is a PON (Passive Optical Network) as an access network system that can achieve both high speed and economy. The PON is a network based on modulation of an optical signal using an optical fiber, and can obtain higher speed than a network using a conventional metal wiring. In addition, in PON, for each communication interface (hereinafter referred to as PON-IF) accommodated in an equipment center, a large number of users can be accommodated only by optical branching by an optical splitter disposed in the middle of the optical fiber line. It can be said that the network is excellent in economic efficiency.

  Conventionally, the mainstream of this PON is a GE-PON (Gigabit Ethernet (registered trademark) PON) that shares a maximum bandwidth of 1 Gbps with 32 users. On the other hand, as a next-generation PON, standardization and research and development of 10 G-EPON (10 Gbps Ethernet (registered trademark) PON), which has a maximum bandwidth of 10 Gbps and can coexist with GE-PON, are being performed. By using this system, an access network that can cope with an increase in the amount of communication traffic can be economically constructed using existing equipment for GE-PON.

  On the other hand, when an optical fiber is multi-branched for accommodating a large number of users, the distance (accessible distance) to a user that can be accommodated in the equipment center is shortened due to a branch loss that occurs at that time. This shortening of the accessible distance means that the equipment centers must be densely arranged according to the user's position distribution, which increases the capital investment and, as a result, one of the excellent features of PON. It will damage the sex. Therefore, even if a large number of users are accommodated in one PON-IF, a device that does not shorten the accessible distance is necessary.

  As a method of solving this problem, there is a method of amplifying an optical burst signal whose intensity is attenuated by an optical amplifier. As a result, the accessible distance can be extended, and an access network that is more economical can be constructed. Patent Document 1 is an example in which an access network is lengthened using an optical amplifier. The present invention is composed of four components: an optical amplifier, an optical bandpass filter (BPF), a feedforward controller, and a variable attenuator (VOA). In particular, the input power to the amplifier in the upstream burst signal varies greatly depending on the installation distance of the ONU and the individual communication lasers. Therefore, the power is detected by the feedforward control unit to increase or decrease the insertion loss amount of the VOA. Is required. The signal amplified by the optical amplifier unit is subjected to automatic level control (ALC: Auto level control) for each burst signal so that the spontaneous emission (ASE) noise is removed by the BPF, and then the power becomes constant at the latter stage of the VOA. ) Function is added. In this case, since the input optical power is monitored in a feedforward manner and only the insertion loss amount of the subsequent variable optical attenuator is determined, the control system becomes simple and the output power can be controlled stably and at high speed. By this mechanism, it is possible to amplify burst signals having various input powers and to optically amplify the signals with a constant output power, thereby realizing a long system.

Japanese Patent No.4834164

  However, in the PX10 standard most widely used in GE-PON, an inexpensive Fabry-Perot laser is used for the ONU side transmission stage in order to reduce the cost. This Fabry-Perot laser has a comb-shaped upward oscillation spectrum in a wide wavelength range of 1310 nm ± 50 nm according to specifications. On the other hand, since a DFB (Distributed feedback) laser is used in the ONU transmission stage of 10G-EPON, it has a steep upward oscillation spectrum of 1270 nm ± 10 nm in terms of specifications. In order to extend the length at the GE · 10G dual rate, it is necessary to amplify the upstream burst signal having these two characteristic spectrums with one optical amplifying device.

  When dual rate amplification of upstream signals of both GE-ONU (PX10) and 10G-ONU is performed with the optical amplifier in Patent Document 1, an optical bandpass filter for ASE noise removal (in accordance with a wide spectrum of GE-ONU (PX10)) The width of (BPF) must be set wide. Therefore, although the 10G-ONU has a steep spectrum, the window width of the optical bandpass filter cannot be reduced, and the signal output from the optical repeater amplifier includes a lot of ASE noise. In other words, in the GE · 10G dual rate, a BPF adapted to the wide wavelength range of the GE-ONU is adopted, and the ASE noise of the 10G-ONU narrow band signal cannot be sufficiently removed. This results in signal quality degradation on the 10G side, and gives a certain penalty to transceiver light sensitivity. As a result, the lengthening effect is reduced or invalidated in the optical amplifier.

  Therefore, in view of the above problems, an object of the present invention is to provide an optical amplifying device that can amplify two optical signals (dual rate) having different standards and extend the length.

  In order to achieve the above object, an optical amplifier according to the present invention has the following two features.

  In the present invention, firstly, with one or more natural numbers n as parameters, one or more demultiplexers capable of demultiplexing an input optical signal with wavelengths of n sections, and an optical signal after wavelength separation for each wavelength section And n optical amplifiers capable of optical amplification, and one or more multiplexers capable of multiplexing optical signals amplified at respective wavelengths.

Specifically, the optical amplification device according to the present invention is:
A duplexer that divides a predetermined wavelength range into n (n is a natural number of 2 or more) wavelength sections, and assigns each wavelength section to n paths;
N optical amplifiers that are arranged for each path and amplify optical signals in wavelength sections allocated to the path;
A multiplexer for multiplexing the optical signals amplified by the optical amplifier in each of the paths;
Is provided.

  This optical amplifying apparatus is high in both a sharp spectrum 10G-ONU and a broad spectrum GE-ONU (PX10) by applying an optical amplifier having different optimum sensitivity / gain for each wavelength to the optical amplifying apparatus. An optimum optical amplifier having a gain can be designed / applied. As a result, even in an upstream signal in which different wavelength spectra are input in a mixed system of GE-PON / 10G-EPON, a high gain can be obtained in a wide wavelength range.

  Therefore, the present invention can provide an optical amplifying device capable of amplifying two optical signals (dual rate) having different standards and extending the length.

  The optical amplifier of the optical amplifying device according to the present invention is characterized in that there is a gain peak in a wavelength section allocated to the path to be arranged. If the maximum sensitivity with respect to the wavelength of each of the n optical amplifiers is designed to be included in each wavelength section, the overall gain of the optical amplification device can be designed to be particularly high.

  Secondly, the present invention removes ASE noise superimposed after optical amplification, so that the transmission bandwidth of either the duplexer, the multiplexer, or both of them is equal to the adjacent wavelength section at the time of wavelength separation. It is characterized by having a window including a certain overlapping section.

  The multiplexer of the optical amplifying device according to the present invention is characterized in that, for each of the paths, there is a window whose transmission band is a wavelength section allocated to the path. In the present optical amplifying apparatus, the transmission band window of the duplexer and multiplexer for cutting off the ASE noise is narrowed to a wavelength region where the optical amplifier connected to the section does not contribute to amplification. Thereby, ASE noise in a wavelength region that does not contribute to amplification can be reduced for each optical amplifier, and deterioration of signal quality of the entire optical amplification device can be suppressed.

An optical amplifying device according to the present invention includes:
A detector that detects the light intensity of the input optical signal input to the duplexer;
An optical attenuator for attenuating the light intensity of the output optical signal output by the multiplexer;
A feedforward control circuit that determines an attenuation amount in the optical attenuator unit so that the optical intensity of the output optical signal becomes a predetermined value according to the intensity of the input optical signal detected by the detection unit;
Is further provided.
The present optical amplifying apparatus can be controlled so as not to cause an excessive output to cause signal distortion or to destroy the transceiver.

  The optical amplification device according to the present invention minimizes the gain of the optical amplifier that amplifies the wavelength section including the center wavelength in the predetermined wavelength range, and increases the gain as the optical amplifier that amplifies the wavelength section far from the center wavelength. It is characterized by being set. Even in the case of an optical signal with a small spectrum at the base, such as a Fabry-Perot laser, by increasing the gain of the optical amplifier that amplifies the spectrum of the base, stable amplification at a dual rate can be achieved without reducing the gain as a whole. Can be realized.

  In the optical amplifying device according to the present invention, at least one of the wavelength sections includes 1260 nm to 1280 nm. This optical amplifying apparatus can be applied as a dual rate optical amplifying apparatus in a mixed system of GE-PON / 10G-EPON.

  The present invention can provide an optical amplifying apparatus capable of amplifying two optical signals (dual rate) having different standards and extending the length.

It is a figure explaining the optical amplifier which concerns on this invention. It is a figure explaining the relationship between the window of the splitter / multiplexer of the optical amplifier which concerns on this invention, and the gain of an optical amplifier. It is a figure explaining the relationship between the gain of the optical amplifier of the optical amplifier which concerns on this invention, and the spectrum of a Fabry-Perot laser. It is a figure explaining the relationship between the window of the splitter / multiplexer of the optical amplifier which concerns on this invention, and the gain of an optical amplifier. It is a figure explaining the optical amplifier which concerns on this invention.

  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. 1 is a diagram illustrating an optical amplifying device 301 according to this embodiment. The optical amplifier 301 is
A demultiplexer 11 that divides a predetermined wavelength range into n (n is a natural number of 2 or more) wavelength sections, and assigns each wavelength section to n paths;
N optical amplifiers 12 that are arranged for each path and amplify optical signals in wavelength sections allocated to the path;
A multiplexer 13 for multiplexing the optical signals amplified by the optical amplifier in each of the paths;
Is provided.

  Consider a case where burst signals from a plurality of connected GE-ONUs and 10G-ONUs are input to the optical amplifying apparatus 301. The GE-ONU has a comb-shaped upstream oscillation spectrum in the wavelength range of 1310 nm ± 50 nm, and the 10G-ONU transmission stage has a steep upstream oscillation spectrum in the wavelength range of 1270 nm ± 10 nm. The center wavelength varies within the specified range.

  The demultiplexer 11 demultiplexes the burst optical signal into n wavelength sections. The input upstream burst signal is demultiplexed by the demultiplexer 11 for each specific section of the wavelength spectrum (λ0 to λ1, λ1 to λ2,..., Λn−1 to λn). For example, when n = 3, λ0 in FIG. 1 is 1240 nm, λ1 is 1260 nm, λ2 is 1280 nm, λ3 is 1300 nm, and the like. If the branching loss at this time is suppressed to 0.5 dB or less, it is desirable from the viewpoint of reducing insertion loss. However, if the gain of the amplifier is large enough to ignore this loss, it does not necessarily have to be less than this branching loss.

  The optical amplifier 12 is arranged for each of a plurality (n) of paths. Here, it demonstrates as an optical amplifier (12-1 to 12-n) for every path | route. The optical signal demultiplexed by the demultiplexer 11 and coupled to each path is optically amplified for each wavelength by the optical amplifier 12. The optical amplifier 12 is, for example, a semiconductor optical amplifier (SOA: Semiconductor optical amplifier) or a fiber amplifier. The amplification factor of the optical amplifier 12 at each wavelength is typically set to 15 dB to 20 dB. If an optical amplifier having this amplification factor is used, it is possible to realize a high lengthening effect of 20 to 40 km in terms of upstream transmission loss. However, if the optimal amplification factor is other than this, taking into account the effect of prolongation, the distribution of equipment centers and users, and the cost required for manufacturing the amplifier, the amplification factor of the optical amplifier can be any value. It does not matter.

  The dynamic range required for the optical amplifier 12 is typically about −30 dB to −10 dB considering that the variation in input power to the connected ONU, which is a feature of the PON, is large at a short distance and a long distance. Is desirable. In this dynamic range, it is possible to give a large degree of freedom to the PON user accommodation design. However, if the cost of the optical amplifier having a high dynamic range is not commensurate with the cost effect with respect to the effect of prolonging the PON, the dynamic range of the optical amplifier may be any value.

  Furthermore, in order to suppress the power penalty at the time of OLT reception, it is desirable that the NF (Noise Figure) of the optical amplifier 12 is typically 10 dB or less. However, the NF of the optical amplifier may be any value if the cost required for the production of the low NF optical amplifier does not match the cost effect with respect to the effect of prolonging the PON.

  The multiplexer 13 multiplexes the optical signals amplified at the respective wavelengths. The multiplexer 13 has a window whose transmission band is a wavelength section allocated to the path for each path. ASE noise is superimposed on the amplified optical signal, and if it is transmitted as it is, the signal quality after amplification is degraded. For this reason, the multiplexer 13 is provided with a window having a wavelength width demultiplexed by the demultiplexer 11, and the signal quality is prevented from deteriorating by removing ASE noise of wavelengths other than the window.

(Embodiment 2)
FIG. 5 is a diagram illustrating the optical amplifying device 302 of the present embodiment. The optical amplifying device 302 has a level control function for adjusting the output level of the amplified optical signal in the optical amplifying device 301 of FIG. Specifically, the optical amplifying device 302 includes:
A detector 14 for detecting the light intensity of the input optical signal input to the duplexer 11;
An optical attenuator 15 for attenuating the light intensity of the output optical signal output from the multiplexer 13;
A feedforward control circuit 16 that determines an attenuation amount in the optical attenuator unit 15 so that the optical intensity of the output optical signal becomes a predetermined value according to the intensity of the input optical signal detected by the detection unit 11;
Is further provided.

  The multiplexer 13 multiplexes and outputs the optical signals amplified for each wavelength, but when controlling so as not to cause excessive output at this time to cause signal distortion or to destroy the transceiver, The output level control function described below is provided.

  This output level control function includes a monitor light extraction coupler 17 inserted in the preceding stage of the optical amplifier 11, a photodiode (detection unit 14) for converting the monitor light into an electric signal, and an optical attenuator based on the intensity of the electric signal. The feed forward control circuit 16 determines the attenuation amount of 15 and the optical attenuator 15 capable of attenuating the optical output from the multiplexer 13 with an arbitrary attenuation amount.

  In the monitoring light extraction coupler 17, about 1% of the input optical signal is demultiplexed and input to a photoelectric conversion photodiode (detection unit 14). If the feedforward control circuit 16 is designed so that the amount of insertion of the optical attenuator at this time is proportional to the potential of the electrical signal for monitoring, the output level of the burst signal is controlled to be constant. Although the coefficient of this proportional control is arbitrary, if it is set so that the output level is approximately +0 to +9 dBm, it is possible to construct an optical amplifying device that can contribute to the extension of the length.

(Embodiment 3)
FIG. 2 is a diagram for explaining the relationship between the transmission wavelength window of the demultiplexer 11 or the multiplexer 13 and the maximum gain of each optical amplifier 12. The optical amplifier 12 has a gain peak in the wavelength section allocated to the path to be arranged. As shown in FIG. 2, if the maximum sensitivity for each wavelength of the n optical amplifiers (12-1 to 12-n) is included in each wavelength section, the overall gain of the optical amplifying device is particularly high. Can be designed.

  For example, if the maximum value of the gain of the optical amplifier in a certain transmission band section is about 20 dB, the design is made such that the gains at both ends of the window are about 17 dB. Further, adjacent windows are overlapped with each other by about 1 to 10 nm in wavelength. By designing in this way, a gain of about 20 dB can be obtained in a wide wavelength band regardless of the ONU type in the entire optical amplifying apparatus, and NF can be kept low.

(Embodiment 4)
FIG. 3 is a diagram for explaining the relationship between the gain of the optical amplifier and the spectrum of the Fabry-Perot laser. The optical amplifying apparatus of this embodiment minimizes the gain of the optical amplifier 12 that amplifies the wavelength section including the center wavelength in the predetermined wavelength range, and increases the gain of the optical amplifier 12 that amplifies the wavelength section far from the center wavelength. Is set.

  Since the DFB laser mounted on the 10G-ONU has a steep and high-intensity spectrum, a sufficiently high gain can be obtained within a single SOA sensitivity range. A Fabry-Perot laser having a broad spectrum cannot cover the sensitivity range of a single SOA, so that it is not possible to increase the gain at the base portion, and as a result, the gain cannot be increased.

  On the other hand, as shown in FIG. 3, if an optical amplifier having a larger gain is arranged in a section away from the center wavelength of the signal group input to the optical amplifying device, a Fabry-Perot laser is provided. The amount of amplification increases at the base of the spectrum. By increasing the gain in the spectrum of the bottom portion in this way, it is possible to realize a stable amplification operation at a dual rate without reducing the gain of the GE-ONU as a whole.

  For example, the oscillation wavelength range on the specification of 10G-ONU is 1260 nm to 1280 nm. Therefore, optical amplification and ASE noise removal are performed with this section as one wavelength section. Since the oscillation wavelength range of GE-ONU includes 1260 to 1360 nm, a section of 1280 nm or more may be divided as another wavelength section to remove optical amplification and ASE noise. In practice, since the GE-ONU Fabry-Perot laser includes a wavelength region other than 1260 to 1360 nm, the wavelength region outside this interval may be amplified.

(Embodiment 5)
FIG. 4 is a diagram illustrating an example of the relationship between the transmission wavelength window of the duplexer 11 or the multiplexer 13 and the maximum gain of each optical amplifier 12. In this embodiment, n = 3, and the wavelength section (transmission wavelength window of the demultiplexer 11 or the multiplexer 13) is 1260 nm to 1280 nm band, 1260 nm or less, and 1280 nm or more, respectively. At this time, when the ASE noise can be ignored in the 1260 nm to 1280 nm band, a high pass filter may be used for forming a window of 1260 nm or less and a low pass filter may be used for forming a window of 1280 nm or more.

  By designing the duplexer 11, the optical amplifier 12, and the multiplexer 13 in this way, it is applicable to a mixed system of GE-PON / 10G-EPON, and is excellent in economic efficiency and has a high gain and low NF. It can be set as a rate optical amplifier.

[Appendix]
The following describes the optical amplification apparatus according to the present invention.
The present invention provides an optimum dual-rate optical amplifying apparatus having a high gain in both a sharp spectrum 10G-ONU and a broad spectrum GE-ONU.

(1):
Using a natural number n of 2 or more as a parameter
One or more demultiplexers capable of demultiplexing an input optical signal with n-section wavelengths;
N optical amplifiers capable of amplifying the optical signal after wavelength separation for each wavelength section;
A dual-rate optical amplifying apparatus comprising: one or more multiplexers capable of multiplexing optical signals amplified at each wavelength in n sections.

(2):
In the dual rate optical amplifying device described in (1) above,
A detection unit for monitoring the intensity of input light at the input unit;
An optical attenuator that can attenuate the light intensity by an arbitrary amount at the output;
A dual-rate optical amplifying device comprising: a feedforward control circuit for determining a variable attenuator insertion loss amount after multiplexing in accordance with the intensity of an input signal to obtain a constant output.

(3):
In the dual rate optical amplifying device according to the above (1) to (2),
A dual-rate optical amplifying device comprising a larger optical amplifier gain in a section farther from the center wavelength of a signal group input to the optical amplifying device.

(4):
In the dual rate optical amplifying device according to the above (1) to (3),
A dual-rate optical amplifying apparatus comprising 1260 nm to 1280 nm in at least one wavelength section.

11: demultiplexers 12, 12-1,..., 12-n: optical amplifier 13: multiplexer 14: detector 15: optical attenuator 16: feedforward control circuit 17: couplers 301, 302: optical amplifier

Claims (6)

A duplexer that divides a predetermined wavelength range into n (n is a natural number of 2 or more) wavelength sections, and assigns each wavelength section to n paths;
N optical amplifiers that are arranged for each path and amplify optical signals in wavelength sections allocated to the path;
A multiplexer for multiplexing the optical signals amplified by the optical amplifier in each of the paths;
An optical amplification device comprising:   The optical amplifier according to claim 1, wherein the optical amplifier has a gain peak in a wavelength section allocated to the path to be arranged.   The optical amplifying apparatus according to claim 1, wherein the multiplexer has a window whose transmission band is a wavelength section allocated to the path for each path. A detector that detects the light intensity of the input optical signal input to the duplexer;
An optical attenuator for attenuating the light intensity of the output optical signal output by the multiplexer;
A feedforward control circuit that determines an attenuation amount in the optical attenuator unit so that the optical intensity of the output optical signal becomes a predetermined value according to the intensity of the input optical signal detected by the detection unit;
The optical amplification device according to claim 1, further comprising:   The gain of the optical amplifier that amplifies the wavelength section including the center wavelength in the predetermined wavelength range is minimized, and the gain is set to be larger for the optical amplifier that amplifies the wavelength section far from the center wavelength. The optical amplifying device according to claim 1.   The optical amplifying apparatus according to claim 1, wherein at least one of the wavelength sections includes 1260 nm to 1280 nm.

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