JPH04369887A - Semiconductor laser module - Google Patents

Abstract

PURPOSE:To provide a semiconductor laser module which is stable in transmission characteristics even if light is reflected at the joint surface of a fiber connector. CONSTITUTION:At least, a semiconductor laser 1 is arranged inside a package 9, and an optical connecting adapter 8 is fixed to the side wall of the package 9. A ferrule 7 is fixed inside the connecting adapter 8, and the end face of the ferrule 7 on a package side is obliquely polished. A semiconductor laser module is formed onto such a constitution that a light takeotut fiber connecting plug 11 is fitted into the optical connecting adapter 8, whereby laser ray emitted from the semiconductor laser 1 is taken out.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser module necessary for optical fiber communication.

0002

2. Description of the Related Art Semiconductor laser modules can be roughly divided into a receptacle type as shown in FIG. 3 and a pigtail type as shown in FIG. The configuration and functions of each will be briefly explained below. First, in FIG. 3, 21 is a semiconductor laser chip, 22 is a SELFOC lens, 23 is a focused beam, 24 is a laser mount, 25 is a monitor photodiode, 26 is a package, and 27 is an optical fiber for extracting laser light. connector plug,
28 is a ferrule, and 29 is a transmission optical fiber. In the receptacle type module configured in this manner, an FC type connector is generally used as the optical fiber connector plug 27 for extracting laser light. In this case, the return light from the tip of the ferrule 28 of the optical fiber connector plug 27 to the laser is large and causes noise generation.

Next, in FIG. 4, 31 is a semiconductor laser chip, 32 is a lens, 33 is a focused beam, 34 is a monitor photodiode, 35 is a thermistor, 36 is a Peltier cooler, 37 is a package, 38 is a ferrule, and 39 is an output. 40 is an optical fiber connector plug. Compared to the receptacle shown in FIG. 2, this type of module has a built-in temperature control function, and is also increasingly equipped with an optical isolator and the like.

0004

However, in the receptacle type connector, the tip of the ferrule 28 of the optical fiber connector plug 27 is FC-polished, so it is difficult to perform digital transmission, etc. in which return light from the end face of the ferrule 28 to the laser is generated. It can be used satisfactorily in systems where the noise level does not significantly affect the transmission characteristics. However, it cannot be applied to systems such as analog transmission where noise level transmission performance is determined. To avoid this, it is possible to prevent the return light from the end face of the ferrule 28 by processing the tip of the ferrule 28 obliquely, but in such an oblique system, the incident angle of light changes slightly each time it is attached and detached. The tracking error increases because of the change.

On the other hand, in the pigtail type, the coupling part between the focused beam 33 and the ferrule 38 is fixed during assembly, so there is no tracking error, and the package 37
The return light from the end face of the inner ferrule 38 to the semiconductor laser chip 31 can also be suppressed by oblique polishing. However, although high-performance optical fiber connector plugs 40 at the fiber tips have been developed in recent years, reflections from the connector joining surface have not been completely eliminated. In our experience with analog transmission systems,
It has been confirmed that the connection condition of the connector plug often causes problems in transmission characteristics. For example, if reflection occurs at the joint surface of the optical fiber connector plug 40, and if the length of the output optical fiber 39 is L, then the period is c/2nL (c: speed of light, n: refractive index of the transmission medium, L : Distance of the point where the returned light is generated) is observed on the spectrum analyzer. This is because multiple reflections occur between the fiber connector joint surface and the laser end face. For example, the output optical fiber 39 configured in the module
Since the length of the transmission line is usually 1 m, periodic noise occurs at approximately 100 MHz intervals, and if a transmission signal exists in that frequency band, the transmission quality will be greatly degraded.

In view of these points, it is an object of the present invention to provide a semiconductor laser module that can obtain stable transmission characteristics even if there is reflection at the fiber connector joining surface.

[0007]

[Means for Solving the Problems] In order to achieve this object, the semiconductor laser module of the present invention includes a semiconductor laser disposed in a package, an optical connector adapter attached to a part of the side wall of the package, and a semiconductor laser module arranged in a package. A package having at least a ferrule fixed in the optical connector adapter and having an obliquely polished end face on the package side, and a fiber connector plug for extracting light emitted from a semiconductor laser fitted to the optical connector adapter; A Peltier cooler and a thermistor to control the temperature of the semiconductor laser placed inside, a monitor photodiode to control the output of the semiconductor laser, an optical lens to focus the semiconductor laser light, and a light to suppress return light. There is also a structure having at least an isolator.

[0008]

[Operation] With the above configuration, high quality transmission can be achieved even if there is reflection at the fiber connector joint surface. That is, when there is light returning to the semiconductor laser, noise is generated at frequency intervals of c/2nL, as described above. In the configuration of the present invention, the fiber connector joint surface where this return light is most likely to occur is located extremely close to the semiconductor laser;
Therefore, the noise generation frequency interval becomes as high as several GHz. Therefore, by setting the transmission band up to several GHz or so as to avoid the frequency band where the noise occurs, transmission with less influence of noise becomes possible.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a configuration diagram of a semiconductor laser module according to an embodiment of the present invention. In FIG. 1, 1 is a semiconductor laser, 2 is an optical lens, 3 is an optical isolator, 4 is a monitor photodiode, 5 is a thermistor, and 6
is a Peltier cooler, 7 is a ferrule, 8 is an optical connector adapter, 9 is a package, and also serves as a transmission system, 10 is a ferrule of a fiber connector plug 11 for optical extraction,
12 is a transmission fiber.

The operation of the semiconductor laser module constructed as described above will be explained below.

Light emitted from the semiconductor laser 1 passes through an optical lens 2 and an optical isolator 3 and is focused on a ferrule 7. Here, the condensing end face of the ferrule 7 is polished obliquely, so that no light returns to the semiconductor laser 1. There are no particular restrictions on the other end of the ferrule 7, but PC polishing is appropriate because it causes less bonding loss. The light that has passed through the ferrule 7 is guided to a transmission fiber 12 by a fiber connector plug 11 for extracting light. Here, the ferrule 7 and the ferrule 7 of the optical fiber connector plug 11 are shown.
If reflection occurs at the junction surface with c
Noise occurs at frequency intervals of /2nL. Here, L is the distance between one end of the semiconductor laser 1 and the junction end of the ferrule 7, which is approximately several mm to 1 cm, and the period of the reflected noise in this case is several GHz to several tens of GHz. If the transmitted signal is, for example, an analog signal and a frequency-multiplexed multi-channel signal, the transmitted signal is received by a photodetector and observed by a frequency component spectrum analyzer, as shown in FIG. 2. It can be seen from this that since the reflective end of the light is close to the laser, the intervals at which reflection noise occurs are very wide, and the transmitted signal is not affected. In the case of the conventional pigtail type, the joint surfaces of the ferrules are separated from the semiconductor laser by about 1 meter, so noise is generated at 100 MHz intervals, degrading the transmission signal.

As described above, according to this embodiment, by arranging the connector joining position of the laser module close to the semiconductor laser 1, high-quality transmission can be performed without the influence of reflected noise.

Although this embodiment has been described using the optical isolator 3 in the module package 9, it is not necessarily necessary depending on the system to which it is applied.

[0014]

As described above, the present invention comprises a semiconductor laser disposed within a package, an optical connector adapter attached to a part of the side wall of the package, and a laser diode fixed within the optical connector adapter whose side end face of the package is fixed. A configuration including at least a diagonally polished ferrule and a fiber connector plug for extracting light emitted from a semiconductor laser that is fitted into an optical connector adapter;
a Peltier cooler and a thermistor for controlling the temperature of the semiconductor laser arranged in the package; a monitor photodiode for controlling the output of the semiconductor laser;
Since some devices have a configuration that includes at least an optical lens for focusing semiconductor laser light and an optical isolator for suppressing return light, it is necessary to directly provide the module with an optical connector adapter that has a built-in ferrule with one side polished diagonally. This allows stable transmission characteristics to be achieved,
A semiconductor laser module with improved transmission characteristics in an analog transmission system can be provided.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a semiconductor laser module in an embodiment of the present invention.

[Figure 2] Diagram showing the relationship between frequency and received light intensity in the same semiconductor laser module

[Figure 3] Configuration diagram of a conventional semiconductor laser module

[Figure 4
] Configuration diagram of other conventional semiconductor laser module

[Explanation of symbols]

1 Semiconductor laser 2 Optical lens 3 Optical isolator 4 Monitor photodiode 5 Thermistor 6 Peltier cooler 7 Ferrule 8 Optical connector adapter 9 Package 10 Ferrule of fiber connector plug for light extraction 11 Fiber connector plug for light extraction 12
transmission fiber

Claims (2)

[Claims] 1. A semiconductor laser disposed in a package, an optical connector adapter attached to a part of a side wall of the package, and a side end surface of the package fixed to the optical connector adapter and polished at an angle. What is claimed is: 1. A semiconductor laser module comprising at least a ferrule with a ferrule and a fiber connector plug for extracting light emitted from the semiconductor laser, which is fitted into the optical connector adapter. 2. A Peltier cooler and a thermistor for controlling the temperature of a semiconductor laser arranged in a package, a monitor photodiode for controlling the output of the semiconductor laser, and a monitor photodiode for focusing the light of the semiconductor laser. 2. The semiconductor laser module according to claim 1, further comprising at least an optical lens and an optical isolator for suppressing returned light.