Patent Publication Number: US-2023155684-A1

Title: Multi-channel light emitting module including lithium niobate modulator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No(s). 202111345406.X filed in China on Nov. 15, 2021, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to optical communication device, more particularly, a multi-channel light emitting module in an optical communication device. 
     Related Art 
     Optical transceivers are generally installed in electronic communication facilities in modern high-speed communication networks. With the improvement of optical communication system and the increase in demand of broad bandwidth by various network services, issues of insufficient internal space and high energy consumption of the conventional optical communication systems need to be tackled. Any solution to provide the small size optical communication systems at minimum expense of internal accommodation space and energy consumption without sacrificing both the bandwidth and transmission speed has been one of the important topics in this technical field. 
     In some optical communication systems for broadband applications, such as data centers and FTTH modems, one or more optical modulators are used to adjust the power, phase, or polarization of the optical signal in order to improve signal transmission efficiency and increase transmission distance. In the conventional optical communication systems, the optical modulator is mostly a silicon-based modulator due to cost considerations, since optical components, such as light emitters, lenses, optical isolators and the like, can be integrated with the silicon-based modulator into a single encapsulation structure for packaging, thereby facilitating miniaturization of the optical communication systems. 
     SUMMARY 
     According to one aspect of the present disclosure, a multi-channel light emitting module includes a base, at least one light emitting unit provided on the base, an optical modulation chip provided on the base, and an optical transmission component. The optical modulation chip includes an encapsulation structure and a thin film lithium niobate (LiNbOx) modulator provided in the encapsulation structure. The thin film LiNbOx modulator is optically coupled with the at least one light emitting unit, and the at least one light emitting unit is provided outside the encapsulation structure. The optical transmission component is optically coupled with the thin film LiNbOx modulator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic view of a multi-channel light emitting module according to one embodiment of the present disclosure; 
         FIG.  2    is a schematic view of a multi-channel light emitting module according to another embodiment of the present disclosure; and 
         FIG.  3    is a schematic view of a multi-channel light emitting module according to still another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. According to the description, claims and the drawings disclosed in the specification, one skilled in the art may easily understand the concepts and features of the present disclosure. The following embodiments further illustrate various aspects of the present disclosure, but are not meant to limit the scope of the present disclosure. 
     A multi-channel light emitting module according to an embodiment of the present disclosure may include a base, at least one light emitting unit and an optical modulation chip. Please refer to  FIG.  1    illustrating a schematic view of a multi-channel light emitting module according to one embodiment of the present disclosure. In this embodiment, a multi-channel light emitting module  1   a  may include a base  10 , at least one light emitting unit  20  and an optical modulation chip  30 . The multi-channel light emitting module  1   a  may be mounted on a driver circuit board  2 . 
     The base  10  may be a carrier for supporting the driver circuit board  2 , and the base  10  may be made of metal for heat dissipation. The light emitting unit  20  may be a laser emitter mounted on the base  10 .  FIG.  1    exemplarily shows that the multi-channel light emitting module  1   a  includes single light emitting unit  20 , while the present disclosure is not limited by the number of light emitting unit  20 . The optical modulation chip  30  may be mounted on the base  10  and include an encapsulation structure  310  and a thin film lithium niobate (LiNbO3) modulator  320  located in the encapsulation structure  310 . The encapsulation structure  310  may be an airtight casing or an electrically insulated dielectric layer for accommodating the thin film LiNbO3 modulator  320 . The thin film LiNbO3 modulator  320  may be optically coupled with the light emitting unit  20 , and the light emitting unit  20  may be located outside the encapsulation structure  310 . 
     A multi-channel light emitting module according to an embodiment of the present disclosure may include a driver chip. As shown in  FIG.  1   , the multi-channel light emitting module  1   a  may include a driver chip  40  electrically connected with the optical modulation chip  30 . Specifically, the optical modulation chip  30  may be electrically connected with the driver chip  40  through pins or gold wires which physically touch the driver circuit board  2 , thereby generating a path for supplying electric power to the optical modulation chip  30  from the driver chip  40  and transmitting modulated signals. The driver chip  40  is located outside the base  10 . In other words, the driver ship  40  is not accommodated inside the base  10 . 
     An optical modulation chip of a multi-channel light emitting module according to an embodiment of the present disclosure may include an optical splitter. As shown in  FIG.  1   , the optical modulation chip  30  may include an optical splitter  330  located at an optical input end  321  of the thin film LiNbO3 modulator  320 . The optical splitter  330  may be accommodated in the encapsulation structure  310 . Alternatively, the optical splitter  330  may be integrated into the optical modulation chip  30 . The optical splitter  330  can split a single input channel wavelength provided by the light emitting unit  20  into four output channels of wavelengths for multi-channel transmission. 
     A multi-channel light emitting module according to an embodiment of the present disclosure may include an optical transmission component. As shown in  FIG.  1   , the multi-channel light emitting module  1   a  may include an optical transmission component  50  mounted on the base  10 . The optical transmission component  50  may be optically coupled with the thin film LiNbO3 modulator  320  of the optical modulation chip  30 , so that optical signals modulated by the optical modulation chip  30  are transmitted from an optical output end  322  of the thin film LiNbO3 modulator  320  through the optical transmission component  50  and received by an external device such as optical connector, optical switch and router. In this embodiment, the optical transmission component  50  may include a fiber array located outside the encapsulation structure  310 . In other words, the fiber array is not accommodated in the encapsulation structure  310 . 
     Also, the multi-channel light emitting module  1   a  may include a heat sink  60 , a collimating lens  70 , an optical isolator  80  and a focusing lens  90 . The heat sink  60  is configured to carry the light emitting unit  20  and help heat dissipation. The light emitting unit  20  is optically coupled with the optical modulation chip  30  through the collimating lens  70 , the optical isolator  80  and the focusing lens  90 . 
     The multi-channel light emitting module  1   a  may be implemented in terms of “one input to four output” typed optical communication. An optical signal emitted by the light emitting unit  20  and propagated in the single input channel is coupled into the optical modulation chip  30 . In the optical modulation chip  30 , the optical splitter  330  splits the optical signal propagated in the single input channel into four optical signals propagated in four independent channels, respectively. The optical signals propagated in the four channels are modulated by the thin film LiNbO3 modulator  320  so as to generate modulated optical signals propagated in the four output channels. The modulated optical signals are output from the thin film LiNbO3 modulator  320  and coupled into four optical fibers  51 , respectively, through the optical transmission component  50  (fiber array). Thereafter, the modulated optical signals are output to the external device(s). 
     A multi-channel light emitting module according to an embodiment of the present disclosure may include a wavelength division multiplexer. Please refer to  FIG.  2    illustrating a schematic view of a multi-channel light emitting module according to another embodiment of the present disclosure. The specific configuration of each component in a multi-channel light emitting module  1   b  and its relative spatial position with respect to other components can be referred to the corresponding component in  FIG.  1   . 
     In this embodiment, the multi-channel light emitting module  1   b  may include a wavelength division multiplexer  30   b  mounted on the base  10 . The wavelength division multiplexer  30   b  may include a plurality of arrayed waveguide gratings optically coupled with the thin film LiNbO3 modulator  320  of the optical modulation chip  30 , and the wavelength division multiplexer  30   b  may be located outside the encapsulation structure  310 . In other words, the wavelength division multiplexer  30   b  may be an external wavelength division multiplexer with respect to the optical modulation chip  30 . 
     In this embodiment, the multi-channel light emitting module  1   b  may include multiple light emitting units  20  with different emission wavelengths.  FIG.  2    exemplarily shows a total of four light emitting units  20  emitting infrared lights in wavelengths peaking at 1270 nm, 1290 nm, 1310 nm and 1330 nm, respectively, and the four light emitting units  20  are configured to be four output channels for the multi-channel transmission. More specifically, each light emitting unit  20  may be an infrared laser emitter. Furthermore, the multi-channel light emitting module  1   b  may include an optical transmission component  51   b  coupled with the optical modulation chip  30 , and the optical transmission component  51   b  may include a single core fiber. 
     The multi-channel light emitting module  1   b  may be implemented in terms of “four input to one output” typed optical communication. The optical signals generated by the four light emitting units  20  are propagated through respective collimating lenses  70 , optical isolators  80  and focusing lenses  90  before being coupled into the optical modulation chip  30 . In the optical modulation chip  30 , the optical signals propagated in the four channels are modulated by the thin film LiNbO3 modulator  320  so as to generate modulated optical signals. The modulated light signals are output from the thin film LiNbO3 modulator  320  and pass through the wavelength division multiplexer  30   b . The wavelength division multiplexer  30   b  may combine the modulated light signals into a single output channel propagated in the optical transmission component  51   b  (such as the single core fiber), before the optical signals are output to the external device(s). 
       FIG.  3    is a schematic view of a multi-channel light emitting module according to still another embodiment of the present disclosure. The specific configuration of each component in a multi-channel light emitting module  1   c  and its relative spatial position with respect to other components can be referred to the corresponding component in  FIG.  1    or  FIG.  2   . 
     In this embodiment, an optical modulation chip  30   c  of the multi-channel light emitting module  1   c  may include a wavelength division multiplexer  340  optically coupled with the thin film LiNbO3 modulator  320 . The wavelength division multiplexer  340  may be accommodated in the encapsulation structure  310 . In other words, the wavelength division multiplexor  340  may be integrated with the thin film LiNbO3 modulator  320  or separately with the same but within the optical modulation chip  30   c.    
     The multi-channel light emitting module  1   c  may be implemented in terms of “four input to one output” typed optical communication. The optical signals generated by the four light emitting units  20  are propagated through respective collimating lenses  70 , optical isolators  80  and focusing lenses  90  and then coupled into the optical modulation chip  30   c . In the optical modulation chip  30   c , the optical signals propagated in the four channels are modulated by the thin film LiNbO3 modulator  320 . The modulated light signals are output from the thin film LiNbO3 modulator  320  and pass through the wavelength division multiplexer  340 . The wavelength division multiplexer  340  may combine the modulated light signals into a single output channel propagated in the optical transmission component  51   b  (such as the single core fiber), before the optical signals are output to the external device(s). 
     The aforementioned specific embodiments describe various multi-channel light emitting modules of either one input to four output or four input to one output, but the present disclosure is not limited thereto. Base on different requirements, the multi-channel light emitting module disclosed therein can be designed in a type of four input to four output or two input to eight output by adjusting the number of light emitting units or providing additional optical splitter. 
     According to the present disclosure, the thin film LiNbO3 modulator is used for the modulation of optical signals, and the thin film LiNbO3 modulator enjoys the advantages of compactness and high modulation efficiency. The optical modulation chip including the thin film LiNbO3 modulator can achieve a high data rate of 100 Gbps or more for the single channel. The optical modulation chip applied to the optical communication system can reduce manufacturing cost and improve signal transmission performance. With the compact thin film LiNbO3 modulator, the multi-channel light emitting module incorporating this LiNbO3 modulator could be small in size. In the meantime, some optical components, such as the light emitting unit, could be moved outside the optical modulation chip instead of being integrating them into the optical modulation chip, to help properly dissipate the heat generated by the optical components. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure. It is intended that the specification and examples be considered as exemplary embodiments only, with a scope of the disclosure being indicated by the following claims and their equivalents.