KR20050029083A - Triplexer optical sub-assembly module with a built-in wdm coupler - Google Patents

Abstract

A triplexer optical module with a built-in WDM optical coupler is provided to use conventional circuit boards and cases for manufacturing the module by adopting the same module structure for the triplexer optical module as the existing diplexer. An optical module is used for an optical subscriber network performing bidirectional digital communication and downlink analog video communication. A laser diode collimating lens(9) converts a light from a laser diode(10) to a polarized light. An optical fiber collimating lens(6) condenses the light passing through a 45 degree filter(8) and a zero degree filter(7) on an optical fiber port(2) in an optical fiber ferrule(1). Alternatively, the optical fiber collimating lens generates a parallel light from an analog downlink signal which is incident on an optical fiber port of a dual-core optical fiber. A non-reflective film(4) reduces reflection loss of the signals. A filter(5) reflects residual downlink digital optical signals. An optical fiber port(3) constitutes a WDM coupler(14) to enhance an optical isolation property.

Description

Triplexer Optical Sub-Assembly Module with a Built-In WDM Coupler

The present invention uses a WDM (Wavelength Division Multiplexing) technique, which uses a downlink digital base band (Basic Band, 1480 nm to 1550 nm) that accommodates a portion of an existing ATM-PON system as a downlink signal, and additional downlink analog In a Broadband Passive Optical Network (BPON) or Gigabit Passive Optical Network (GPON) system based on ITU-T Regulation G.983.3, which has been assigned an Enhancement Band (1539nm to 1560nm) to accommodate video broadcast or data signals. The present invention relates to a triplex optical module that can be used, and more particularly, to a triplexer optical module integrating an internal WDM coupler that separates two optical signals in separating an analog video broadcasting signal of an enhancement band from a digital basic band. . In particular, the triplex with a built-in WDM coupler of the present invention uses a dual core optical fiber ferrule to manufacture a WDM coupler that separates the downlink digital base band and the downlink analog reinforcement band, so that the size of the optical module is ATM-PON. It can be maintained similar to the optical module for use, and can also be manufactured without degrading the optical cross-talk (Optical Cross-talk) characteristics between the digital optical signal and the analog optical signal.

The present invention provides a WDM (Wavelength Division Multiplexing) for an optical passive network in accordance with the ITU-T G.983.3 standard for accommodating not only two-way digital optical communication such as the Internet but also analog optical signal distribution such as CATV through one optical fiber. The present invention relates to an analog signal optical fiber splitter optical module (Optical Sub-Assembly) with a built-in coupler.

The existing ATM-PON optical subscriber network uses two optical wavelengths as up-down signals, and for this purpose, a wavelength coupler, a laser diode, and a digital receiver are integrated in one body, which is called a diplexer. In addition to the existing diplexer function, the triplexer adds an analog optical receiver part because it must accommodate analog signal distribution. Such a triplexer includes three optical wavelength bands in addition to the wavelengths allocated to the two digital signals, including the wavelength bands for the analog optical signal.

Therefore , all three optical signal bandwidths exist in a system that accommodates analog optical signal distribution, and the bandwidths of the main optical signals defined in ITU-T G.983.3 are uplink digital optical signals (1260-1360 nm) sent from the subscriber. , Downlink digital optical signals (1480-1500 nm) including data and IP signals, downlink analog optical signals (1550-1560 nm) for distributing video signals such as CATV.

Compared to the conventional diplexer for bidirectional communication, the diplexer consists of a laser diode (LD) for uplink signal and a digital receiver (PIN-TIA) for receiving downlink digital signal. Since the downlink analog optical signal distributed in the existing diplexer has to be accommodated, a part for separating and receiving the analog optical signal from the digital optical signal must be added.

Such a triplexer can be generally divided into three stages according to the degree of integration.

1) WDM coupler external triplexer: WDM coupler for separating digital and analog optical signals is located outside the device, the analog receiver is also located outside (see Figure 1).

2) WDM coupler built-in triplexer: WDM coupler for separating digital and analog optical signals is integrated inside the device, and the analog receiver is located outside (see Fig. 2).

3) Integrated triplexer: A light source, a digital receiver, and an analog receiver are all integrated in one optical module (see FIG. 3).

Ultimately, integrated triplexers are expected to dominate the mainstream, but in intermediate or specific systems, separate triplexers with external or embedded WDM couplers are expected to be used. A separate triplexer can be used if an already established subscriber system is difficult to apply an integrated triplexer directly or if the analog and digital signals are to be processed in separate circuits.

These triplexers, including all three optical wavelength bands, must satisfy both the optical and electrical characteristics of digital and analog, which makes the design and fabrication process more diverse and difficult. Compared to the WDM coupler external type, the triplexer having the WDM coupler for the analog signal of the present invention has advantages such as price / size / efficiency of operation.

Accordingly, the present invention is to solve the above-mentioned conventional problems, by integrating the WDM coupler inside the optical module without deteriorating overall characteristics such as optical isolation between the digital optical signal and the analog optical signal, the entire optical module The aim is to provide an analog signal optical fiber splitting triplexer optical module with a built-in WDM coupler that reduces the cost and reduces the size.

Optical fiber split type triplexer optical module with a built-in WDM coupler according to the present invention for achieving the above object is an optical module for use in an optical subscriber network system for receiving a two-way digital transmission and reception and analog video distribution signal, the laser diode and The laser diode collimating lens converts the light emitted from the laser diode into balanced light, and focuses the light transmitted through the 45 degree filter and the 0 degree filter to the optical fiber port 2 of the dual core fiber ferrule, or the dual input unit. An optical fiber collimating lens that makes the analog down-signal incident to the optical fiber port 2 of the core optical fiber balanced, an antireflection thin film that reduces the reflection loss of each signal and makes the optical fiber port on the same focal plane for the optical fiber collimating lens; When passing only the optical signal and reflecting the remaining digital optical signal The key has an optical fiber port 3 with a filter attached to increase the optical isolation of the analog signal, using a wavelength band of 1260 nm to 1360 nm as an uplink digital signal, and a wavelength band of 1480 to 1500 nm as a downlink digital signal. And constructing a triplexer using a wavelength range of 1550-1560 nm as a downlink analog optical signal, and fabricating a WDM coupler using a dual core optical fiber ferrule to separate the digital optical signal from the analog optical signal. It features.

In addition, in order to minimize the insertion loss of the analog optical signal and to increase the optical isolation of the analog optical signal with respect to the digital signal, the dual antireflective coating block having the same thickness and a filter that transmits only the analog optical signal are dual separately. It is another feature to attach to the core fiber ferrule end surface.

In addition, a filter for transmitting only the antireflective coating block and an analog optical signal is manufactured on one glass surface, and then two parts are manufactured on one substrate by chemical etching or mechanical polishing through some photolithography of the filter surface. It is another feature to attach to the cross-section of the dual core optical fiber ferrule.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

4 is an overall schematic diagram of an optical fiber split type triplexer optical module incorporating a WDM coupler of the present invention, and the operation principle according to the three types of related optical signals is as follows.

First, in the case of the digital down signal, the digital down signal incident on the optical fiber port 2 of the dual core optical fiber ferrule 1 of the input portion passes through the anti-reflection thin film 4 and is balanced by the optical fiber collimating lens 6. Made of light It then passes through filter 7 and is reflected by filter 8 at 45 degrees. Finally, the balanced light is focused by the receiver collimating lens 11 to the digital optical receiver and detected. At this time, the filter 11 is for removing the downward analog signal remaining in the digital signal and the upward digital signal from the laser diode.

In the case of the digital uplink signal, the light emitted from the laser diode 10 is converted into a balanced light by the laser diode collimating lens 9 and then through the 45 degree filter 8 and the 0 degree filter 7 to the optical fiber collie. It is focused by the mating lens 6 and coupled to the optical fiber port 2 of the dual core ferrule 1. In this case, the coupling efficiency from the laser diode 10 to the optical fiber is determined by the effective focal length ratio of the laser diode collimator 9 and the optical fiber collimator 6.

In the case of the analog downlink signal, the analog downlink signal incident on the optical fiber port 2 of the dual core ferrule 1 of the input unit is made into balanced light by the optical fiber collimating lens 6. After being reflected by the filter 7, it is focused by the optical fiber collimating lens 6 and then coupled to the optical fiber port 3. At this time, the optical fiber port 3 passes only the analog optical signal and attaches a filter for reflecting the remaining digital optical signal to increase the optical isolation of the analog signal. At this time, the antireflection thin film 4 not only reduces the reflection loss of each signal but also serves to keep the optical fiber ports 2 and 3 on the same focal plane with respect to the optical fiber collimating lens 6.

The main features of the present invention are 1) the use of dual core optical fiber ferrules to separate analog optical signals from the triplexer, and 2) the antireflective thin film 4 and the filter (5) separately manufactured on the optical fiber ferrules such as epoxy By using an adhesive to attach, this is a simple process compared to the method of coating a thin film directly on the ferrule, there is an advantage that can reduce the price of the device.

In the case of attaching a filter using the epoxy proposed in the present invention, as shown in FIG. 6, a method of separately manufacturing and attaching the antireflective thin film 4 and the filter 5, and as shown in FIG. 7, There may be two methods of fabricating the filter on one glass surface to remove a portion of the filter surface to simultaneously produce the antireflective thin film 4 and the filter 5 on one substrate.

FIG. 5 is a side cross-sectional view of the dual core ferrule to which the filter 5 and the antireflective thin film 4 are attached, and FIG. 6 is a structural diagram of the filter of the filter 5 and the antireflective thin film 4 attached to the dual core ferrule.

FIG. 6 illustrates a case in which the filter 5 and the antireflective thin film 4 are separately formed. In the antireflective thin film 4, the contact surface of the optical fiber ferrule is a glass surface similar in refractive index to the optical fiber, and the contact surface of the air reduces reflection. For anti-reflective coating cotton. In the case of the filter 5, the surface in contact with the optical fiber is a filter coating surface for separating wavelengths, and the surface in contact with air is also an antireflection coating surface for reducing reflection loss.

FIG. 7A is a filter structure diagram when the filter 5 and the antireflective thin film 4 of FIG. 6 are fabricated on the same substrate, and FIG. 7B is an exemplary process of fabricating using a mechanical polishing method, and FIG. 7C is a chemical etching process. Process illustration for the case of making.

As shown in the drawing, a filter and an antireflection thin film are simultaneously manufactured on one glass substrate. As shown in the figure, a part of the filter coating surface is removed through chemical etching or mechanical polishing after the filter is manufactured. If the removed side is later bonded to the fiber ferrule, the use of an index matching epoxy, which is the same refractive index as glass, can prevent loss due to scattering on the etched or polished surface from which the filter is removed.

(Example)

The following is an embodiment designed and manufactured WDM coupler built-in triplexer of the present invention.

First, the characteristics of each part such as the lens used in the design and manufacture are as follows.

Dual core optical fiber ferrule (1): Ceramic ferrule with a spacing of 250 mu m between optical fiber ports (2) and (3).

Antireflective thin film (4): 0.5mm glass block with antireflection coating at 1260 ~ 1560nm wavelength

Analog signal transmission filter (5): A digital signal reflection / analog signal transmission filter having a thickness of 0.5 mm equal to that of an antireflective coating block, and having an optical isolation of ˜-30 dB with a digital signal.

Optical fiber collimating lens 6: Aspherical lens with an effective focal length of 4.02 mm (at 1550 nm).

Analog Optical Signal Reflection Filter 7: A digital signal transmission / analog signal reflection filter, wherein the optical isolation with the digital signal is -3OdB.

Up and down digital signal separation 45 degree filter (8): A filter for separating up and down digital signal at 45 degrees. The ad gradation between the digital signals is ~ -20 dB.

Laser diode collimating lens 9: Aspherical lens with an effective focal length of 1.5 mm (at 1310 nm).

Laser Diode (10): 1310nm Fabric-Perot (FP) laser diode operating at 155Mbps.

Downlink digital signal transmission filter 11: A filter that transmits only a downlink digital signal, and its optical isolation with other signals is ˜-30 dB.

Digital receiver collimating lens 12: an aspherical lens with an effective focal length of 4.02 mm (at 1550 nm).

Digital Optical Receiver (13): InGaAs PIN-TIA Operating at 622Mbps

Analog Optical Signal Separator 14: Part of the built-in WDM coupler block that functions to separate analog optical signals from digital optical signals.

FIG. 8 is a detailed design diagram of an input unit using a dual core ferrule as an embodiment of the present invention, and illustrates a WDM coupler portion separating the digital optical signal and the analog optical signal from the input unit. The optical signal incident on the optical fiber port (2) passes through the optical fiber collimating lens (6) and is converted to the balanced light, and proceeds with an inclination angle of about 1.8 degrees due to the 125 μm off-set at the central axis of the lens, and then the optical fiber After being reflected by the analog optical signal reflection filter 7 located at the effective focal length of the collimating lens 6, it is again focused by the optical fiber collimating lens 6 and coupled to the optical fiber port 3. The anti-reflective thin film 4 minimizes the reflection loss of the optical signals, and the analog optical signal transmission filter is for increasing the advertisement degree of the digital signal and the analog optical signal. At this time, the optical thicknesses of the antireflective block 4 and the filter 5 should be the same so that the two optical fiber ports 2 and 3 are raised on the same hyperplane of the optical fiber collimating lens.

9 is a diagram illustrating a design of an optical path of an uplink digital signal of the present invention.

Since the effective focal length of the laser diode collimating lens 9 is 1.5 mm and the effective focal length of the optical fiber collimator lens 6 is 4.02 mm, the magnification for the laser diode beam size determined by the two lenses is four times. Therefore, since the beam diameter of the laser diode is 1.5-2 μm, the optical fiber coupling efficiency of the laser diode of about 40-50% is obtained by calculating that the single mode beam diameter of the single mode optical fiber is ˜10 μm.

10 is a diagram illustrating a design of an optical path of a downlink digital signal of the present invention.

The effective focal length of the receiver collimating lens 12 used in the optical receiver is 4.02 mm, which is equal to the effective focal length of the optical fiber collimating lens. Thus, the downward digital optical signal from the optical fiber port 2 is focused on the receiver with the same size as the optical fiber beam diameter. Since the size of the PD chip used in the receiver is 40 ~ 80um, all the focused light can be focused in the active area of the PD chip.

FIG. 11 is a diagram illustrating a use state of the present invention, which is a three-dimensional schematic diagram of an actual designed WDM coupler-embedded triplexer using an outer mechanism. The fabricated triplexer was able to achieve about -30dB of isolation between the digital and analog signals, and the insertion loss of the analog signal was ~ 1.5 dB. In addition, PIN-TIA received a sensitivity of -35dBm and a laser diode output of 0dBm or more.

Although the preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the above-described embodiments, and the present invention is not limited to the above-described embodiments without departing from the spirit of the present invention as claimed in the claims. Various modifications can be made by those skilled in the art, and such modifications are intended to fall within the scope of the appended claims.

As described above, the optical fiber split type triplexer optical module incorporating the WDM coupler according to the present invention is characterized by separating analog signals using dual core ferrules. Compared to the general diplexer used for PON), since the structure and size of the device do not change much, there is an advantage that the same circuit board and case as the transceiver used in the conventional diplexer can be used when fabricating the module. In addition, the filter is attached to the cross section of the ferrule in order to increase the advertisement clarity of the analog signal, thereby reducing the price by eliminating the need for an additional filter externally.

1 is a block diagram of a typical WDM coupler external triplexer optical module .

2 is a block diagram of a typical WDM coupler built-in triplexer optical module .

3 is a block diagram of an integrated triplexer module with a typical WDM coupler / analog receiver;

Figure 4 is an overall schematic diagram of an analog signal optical fiber split triplexer optical module with a WDM coupler of the present invention.

Figure 5 is a side cross-sectional view of the dual core ferrule attached filter and antireflective thin film.

6 is a structural diagram of a filter and an antireflection thin film attached to a dual core ferrule.

7A is a structural diagram of a thin film prepared on the same substrate with the filter and the antireflective thin film of FIG. 6;

Figure 7b is an illustration of a process produced by using a mechanical polishing method.

7C is an exemplary process for the case of making by chemical etching.

8 is a detailed design of the input unit using a dual core ferrule as an embodiment of the present invention.

9 is a diagram illustrating a design of an optical path of an uplink digital optical signal of the present invention.

10 is a diagram illustrating a design of an optical path of a downlink digital optical signal of the present invention.

11 is a use state diagram of the present invention.

<Explanation of symbols for main parts of drawing>

1: Dual core optical fiber ferrule

2, 3: fiber optic port

4: antireflective thin film for phase down signal

5: Phase downward digital signal reflection / downward analog signal transmission 0 degree filter

6: fiber collimating lens

7: 0 degree filter for transmitting phase down digital signal and reflecting down analog signal

8: 45 degree filter for upstream digital signal transmission / downward digital signal reflection

9: laser diode collimating lens

10: laser diode

11: Upward digital, downlink analog signal reflection / downward digital signal transmission 0 degree filter

12: Digital Receiver Collimating Lens

13: digital optical receiver PIN-TIA

14: WDM coupler block at input

Claims (10)

An optical module for use in an optical subscriber network for receiving two-way digital transmission and reception and a downlink analog video distribution signal, A laser diode 10, a laser diode collimating lens 9 for converting the light emitted from the laser diode 10 into a balanced light, and passed through a 45 degree filter 8 and a 0 degree filter 7 An optical fiber collimating lens (6) for focusing light to the optical fiber port (2) of the dual core optical fiber ferrule (1) or for equilibrating the analog downward signal incident to the optical fiber port (2) of the dual core optical fiber of the input unit; Reflects only the non-reflective thin film 4 and the analogue downlink optical signal, which reduce the reflection loss of each signal and keep the optical fiber ports 2 and 3 on the same focal plane with respect to the optical fiber collimating lens 6, and reflect the remaining downstream digital optical signal. The optical signal splitting optical splitter module with a built-in WDM coupler (14) comprising a fiber port (3) having a filter (5) attached to the optical signal to increase the optical isolation of the analog signal. The method of claim 1, The bidirectional digital transmit / receive signal uses a wavelength band of 1260 nm to 1360 nm as an uplink digital optical signal, a wavelength band of 1480 to 1500 nm as a downlink digital optical signal, and an analog optical signal uses a wavelength band of 1550 to 1560 nm as a downlink analog optical signal. Fiber optic split triplexer optical module with integrated WDM coupler. The method of claim 1, Both sides of the antireflective thin film 4 are made of a glass substrate and an antireflective coating surface, and the filter 5 is composed of a dual core optical fiber ferrule comprising an antireflective coating surface on one side of the glass surface and a filter coating surface on the other side ( A triplexer optical module having a WDM coupler 14 using 1). The method according to any one of claims 1 to 3, In order to minimize the insertion loss of the analog optical signal and to increase the optical isolation of the analog optical signal with respect to the digital signal, an antireflection thin film 4 having the same thickness and a filter 5 for transmitting only the analog optical signal are provided. A triplexer optical module having a WDM coupler (14) using dual core optical fiber ferrules (1), characterized in that attached separately to the dual core optical fiber ferrule cross section. The method of claim 4, wherein WDM coupler characterized in that the antireflection thin film 4 and the filter 5 are attached to the dual core optical fiber ferrule 1 by using an index matching epoxy which is the same refractive index as glass when attaching to the dual core optical fiber ferrule cross section. A triplexer optical module having 14. The method according to any one of claims 1 to 3, The antireflective thin film 4 and the filter 5 which transmits only an analog optical signal are manufactured by forming the filter 5 on one glass surface, and then, two parts of the filter surface are subjected to chemical etching or mechanical polishing through photolithography. A triplex optical module having a WDM coupler (14), characterized in that a part of the substrate is produced by attaching to the cross-section of the dual core optical fiber ferrule (1). Both sides of the antireflective thin film 4 are made of a glass substrate and an antireflective coating surface, and the filter 5 is composed of a dual core optical fiber ferrule comprising an antireflective coating surface on one side of the glass surface and a filter coating surface on the other side ( WDM coupler 14 using 1). The method of claim 7, wherein In order to minimize the insertion loss of the analog optical signal and to increase the optical isolation of the analog optical signal with respect to the digital signal, an antireflection thin film 4 having the same thickness and a filter 5 for transmitting only the analog optical signal are provided. A WDM coupler (14) using dual core optical fiber ferrules (1), characterized in that they are attached separately to the dual core optical fiber ferrule cross sections. The method of claim 8, The WDM coupler 14 attached to the dual core optical fiber ferrule 1 using an index matching epoxy having the same refractive index as glass when the antireflective thin film 4 and the filter 5 are attached to the dual core optical fiber ferrule cross section. . The antireflective thin film 4 and the filter 5 produce a filter 5 on one glass surface, and then apply a part of the filter surface to a single substrate by chemical etching or mechanical polishing through photolithography. A method for manufacturing the WDM coupler (14) according to any one of claims 7 to 8, characterized in that it is manufactured and attached to the cross section of the dual core optical fiber ferrule (1).