KR20190002920A - Optical receiver with at least two wavelength tunable filter - Google Patents

Abstract

The present invention relates to an optical receiver using at least two wavelength tunable filters which uses at least two wavelength tunable filters in channels having a plurality of wavelengths to separate a channel having a specific wavelength to receive the channel. The optical receiver is a wavelength tunable optical receiver, and comprises: two etalon filters (510, 520) arranged on a propagation path of an optical signal; and a lens (200) and a light-receiving photodiode (300) arranged on an optical path passing through the two etalon filters (510, 520) to minimize a temperature change required for wavelength tuning to lower a maximum temperature of etalon filters in comparison to a conventional optical receiver with a single etalon filter, and increase the thickness of etalon filters to improve mechanical stability of the etalon filters.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an optical receiver using at least two wavelength tunable filters,

The present invention relates to an optical receiver using a tunable filter, and more particularly, to an optical receiver using two or more wavelength tunable filters for separating and receiving a channel having a specific wavelength by using two or more tunable filters in a channel having a plurality of wavelengths. To an optical receiver using the same.

Recently, communication services such as a video service of a smart phone and the like have been introduced with a great communication capacity. Accordingly, there is a need to significantly increase the conventional communication capacity. As one of the communication capacity increasing methods, a WDM (Wavelength Division Multiplexing) communication method using an optical fiber that has been conventionally installed has been adopted have. The WDM uses a phenomenon in which laser beams having different wavelengths do not interfere with each other, so that even if a plurality of wavelengths of light are simultaneously transmitted through one optical fiber, there is no interference between signals. Transmission method.

The NG-PON2 specification sets the wavelengths of 4 channels or 8 channels as a downlink optical signal from a telephone office to a subscriber. In this NG-PON2 standard, NG-PON2 (Next Generation-Passive Optical Network version 2) The wavelength spacing of these channels is set to 50 GHz, 100 GHz, or 200 GHz with equal spacing.

In this NG-PON2 standard, one subscriber must select one wavelength and receive light. The separation of such wavelengths is a fixing device for separating the wavelengths. By inputting a channel optical signal of a specific wavelength to the optical receiver, It is possible to receive it. However, in the optical receiver in which the fixed wavelength is separated into a specific optical fiber and the optical reception is performed irrespective of the type of the wavelength coupled to the specific optical fiber, the allocation of the optical line is not performed dynamically, so that it has been difficult to manage the optical line.

Recently, high-definition, high-capacity video communication has been transformed into mainstream contents. In the United States and other countries, competition is taking place to preempt the next generation optical communication networks. In this competition, cable companies such as Comcast, Internet companies such as Google, Verizon Have all started to compete based on optical communication. In the United States, Comcast has begun to expand its high-speed fiber-optic network throughout the United States in order to provide video-based services. In addition, Google is expanding its fiber-optic network by converting Google fiber, Verizon has commercialized the world's fastest 40Gbps downlink 10Gbps TWDM-PON (time-wavelength division multiplexing) technology to meet the challenges of cable and Internet companies. In addition, Japan's NTT plans to introduce 40Gbps downward 40Gbps TWDM-PON technology in 2018 with Japan's Oki, and China is also introducing downward 40Gbps and upward 40Gbps TWDM-PON .

In this way, worldwide subscriber networks require enormous data traffic in order to service congested data traffic, such as high AR (Augmented Reality) VR (Virtual Reality), with existing optical fiber, and maximize efficiency of optical fiber (Time-wavelength multiplexing) technology that can be used in a wide range of wavelengths.

In the TWDM-PON system, one optical module of four stations and a corresponding number of optical modules (1:32 or 1:64) of the subscriber are interlocked. The optical receiver module of the subscriber should select the wavelength to communicate with the designated wavelength among the channels having a wavelength interval of 0.8 nm (100 GHz @ 1550 nm), and the rate of such variable wavelength has a great influence on the application of the system It goes crazy. The current NG-PON2 standard uses 100GHz wavelength spacing of 4 channels, but the International Organization for Standardization (ITU-T) defines TWDM-PON using up to 8 channels of 100GHz wavelength spacing.

A silicon etalon filter is used as a wavelength selective filter for receiving such a tunable light. However, the silicon etalon filter has a wavelength variability of 10 GHz / ° C, which requires a temperature change of at least 70 ° C to vary the eight channels. Since the wavelength tunable optical receiver must operate at an external environment temperature of at least 70 ° C, the temperature of the tunable filter should be changed to at least 90 ° C to 160 ° C when a thermoelectric device is not used. Also, in case of using a thermoelectric element, it is preferable that the set temperature of the thermoelectric element is 50 ° C or more when the external environment temperature is 70 ° C in terms of power consumption of the thermoelectric element. In this case, ℃.

When a thermoelectric device is used, the maximum temperature of the etalon filter reaches at least 120 ° C., and when the thermoelectric device is not used, the maximum temperature of the talon filter reaches at least 160 ° C. Such a high temperature brings about a great difficulty in the stability of the etalon filter and the method of attaching the etalon filter.

In order to select eight channels using one filter, the FSR (free spectral range) of the filter must reach at least 800 GHz, and the thickness of the silicon etalon filter having the FSR is about 45 μm. Such a thin etalon filter is difficult to use due to the low mechanical strength of the etalon filter.

U.S. Pat. No. 6,985,281 (Oct. 10, 2006) Korean Patent Publication No. 10-2016-0128599 (Aug.

The present invention has been made in order to solve the above problems of the prior art, and it is an object of the present invention to provide a wavelength tunable filter which can minimize the temperature change required for wavelength tuning and change the maximum temperature of the etalon filter, And to increase the mechanical stability of the etalon filter by increasing the thickness of the etalon filter.

According to an aspect of the present invention, there is provided an optical receiver in a wavelength tunable optical receiver, wherein two etalon filters are disposed on a propagation path of an optical signal, And a light receiving photodiode are disposed.

Here, the two etalon filters each have a built-in heater, or at least one of the two etalon filters has a built-in heater, and the temperature of the other etalon filter can be controlled by the thermoelectric element .

It is also preferable that the FSR (Free Spectral Range) of the etalon filter whose temperature is controlled by the thermoelectric element is larger than the FSR of the etalon filter whose temperature is controlled by the heater.

According to the present invention, for example, when two etalon filters have FSR of 300 GHz and FSR of 400 GHz, all the channels can be selectively set when the temperature of the etalon filter is changed at 50 to 90 ° C, And the thickness of each of the etalon filters has a thickness of 90um and 120um, which is an effect to increase the mechanical stability compared to the method using one etalon filter having a conventional 45um thickness have.

FIG. 1 is a conceptual diagram of a wavelength tunable optical receiver in which a wavelength is variable,
2 shows an embodiment of a wavelength tunable receiver having two etalon filters proposed in the present invention,
3 shows an example of the etalon filter temperature at the time of CH1 selection,
Fig. 4 shows an example of the etalon filter temperature at the time of selecting CH5,
5 shows an example of the etalon filter temperature when CH8 is selected.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. It is to be understood that the term "comprises" or "having" in the present application does not preclude the presence or addition of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification .

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, an optical receiver using a tunable filter according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a conceptual diagram of a wavelength tunable optical receiver in which a wavelength is variable when a conventional filter is used.

As shown in FIG. 1, in general, an optical receiver includes a thermoelectric element 100, a lens 200, a light receiving element 300, a light ray 400 entering the optical receiver, and a structure having one etalon filter And an etalon filter 500 of FIG. In the optical receiver, a TIA (Transimpedance amplifier), a capacitor, and the like can be further added. The etalon filter transmits only the resonant wavelength with the etalon filter and reflects the other wavelengths. The light ray 400 that is introduced into the optical receiver from the 8-channel DWDM is composed of eight wavelengths, and only the optical signal having the wavelength component transmitted through the etalon filter is transmitted through the etalon filter 500. It is preferable that the light rays guided to the etalon filter 500 are collimated parallel rays, and the light rays transmitted through the etalon filter 500 are also parallel rays. The parallel light transmitted through the etalon filter 500 is converged through the lens 200 and reaches the light receiving area of the light receiving element 300 to be converted into an electric signal. The light receiving element 300 may be a PIN-photo diode having a PIN structure or an avalanche photo diode (APD).

1, an etalon filter 500 is attached to the thermoelectric element 100, and the temperature of the etalon filter 500 is adjusted by the thermoelectric element 100. In this case, Therefore, in the conventional structure of FIG. 1, the optical signals of CH1 to CH8 can be exclusively selected and received by changing the temperature of the thermoelectric element from 50 to 120 deg. At this time, the etalon filter 500 must have an FSR of at least 800 GHz. In this case, the thickness of the etalon filter is about 45 um, which is very thin, which is very weak against vibration or impact.

2 shows an embodiment of a wavelength tunable receiver having two etalon filters proposed in the present invention.

2, in the structure of the present invention, the first etalon filter 510 is directly attached to the thermoelectric element, the second etalon filter 520 has a heater, It is preferable to be attached via the heat resistant object 600.

In one embodiment, the first etalon filter 510 has a FSR of 400 GHz and the temperature is controlled by a thermoelectric element, and the second etalon filter 520 is controlled by a thermoelectric element and a self- . At this time, the second etalon filter 520 must be at the same temperature or higher than the first etalon filter 510. It is preferable that the FSR of the filter in the higher temperature region is smaller than the FSR of the filter in which the temperature is set to the lower temperature. In this case, it is preferable that the FSR of the first etalon filter 510 whose temperature is controlled only by the thermoelectric element 100 is larger than the FSR of the second etalon filter 520 whose temperature is controlled by the thermoelectric element and the heater Do.

Fig. 3 shows an example of the etalon filter temperature when CH1 is selected, Fig. 4 shows an example of the etalon filter temperature when CH5 is selected, and Fig. 5 shows an example of each etalon filter temperature when CH8 is selected.

First, assume that CH1 is set at 50 DEG C for each of the etalon filters 510 and 520 to set CH1 in FIG. Since the silicon etalon filter has a wavelength variability of 10 GHz / 占 폚, CH2 is selected when the temperature of each etalon filter 510, 520 is all 60 占 폚. In this way, CH5 in FIG. 4 is set when the first etalon filter 510 is at 50 DEG C and the second etalon filter 520 is at 60 DEG C. [ Further, in the case of setting CH8 in Fig. 5, the first etalon filter 510 is set at 80 DEG C and the second etalon filter 520 is set at 90 DEG C. [

Therefore, when two etalon filters are used, all eight channels can be selected by varying the temperature of the etalon filter only from 50 ° C to 90 ° C. In this description, the setting of CH1 at 50 DEG C is for explanation only, and any other temperature may be set. That is, in the case of using only one etalon filter 500, all the channels can be exclusively selected when the temperature change width of the filter reaches 70 ° C., while the two etalon filters 510 and 520 It is possible to access all the channels even if the temperature change range of the filter is changed only by 40 ° C. Also, in this example, the etalon filters 510 and 520 having FSRs of 800 GHz and 400 GHz and 300 GHz, respectively, have thicknesses of 90 and 120 μm, respectively, as compared with the 45 μm etalon filter 500, thereby increasing the mechanical stability.

In the present invention, the case where the FSR of the first etalon filter 510 whose temperature is controlled by the thermoelectric element is larger than the FSR of the second etalon filter 520 whose temperature is controlled by the heater is exemplified, The maximum temperature to be regulated should be changed to 100 ° C higher than 90 ° C in the case described above. This is caused by the constraint condition that the temperature 520 of the second etalon filter 520 should be at least equal or higher than the first etalon filter 510.

100: thermoelectric element
200: lens
300: light receiving element
400: incoming optical signal beam
500: etalon filter with one etalon filter
510: Ettalon filter with wide FSR with two etalon filters
520: Ettalon filter with narrow FSR with two etalon filters
600: heat resistant object

Claims (4)

In a wavelength tunable optical receiver,
Two etalon filters 510 and 520 are disposed on the optical path of the optical signal,
Wherein a lens (200) and a light receiving photodiode (300) are disposed on an optical path passing through the two etalon filters (510, 520).
The method according to claim 1,
Wherein the two etalon filters (510) and (520) each incorporate a heater.
The method according to claim 1,
Wherein at least one etalon filter of the two etalon filters (520) and (520) embeds a heater, and the temperature of the other etalon filter is controlled by the thermoelectric element (100) receiving set.
The method of claim 3,
Wherein the free spectral range (FSR) of the etalon filter whose temperature is controlled by the thermoelectric element (100) is larger than the FSR of the etalon filter whose temperature is controlled by the heater.

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