This study deals with quantum dot laser-diodes (QD-LDs). The influence of highly stacked quantum dot (QD) layers in QD-LDs on the laser characteristics through experiments and numerical calculations is reported and the optimal design for the QD-stacked layer numbers is indicated. By introducing new concepts, the previously reported carrier rate equations are modified in order to include the effect of the stacked QD layer numbers. It is confirmed that the threshold current and slope efficiency between fabricated and calculated QD-LDs are almost the same. Considering low threshold current, high output power, and high slope efficiency, the optimal design of the QD-stacked layer number in our QD-LD is supposed to be 14. With this, a threshold current of 38 mA, maximum optical output power of 22.7 mW, and slope efficiency of 0.28 W/A can be obtained from the QD-LD. equipment such as industrial equipment and sensors via the Internet, Machine to Machine (M2M) technology, which shares information between industrial machines, and the edge computing, which instantaneously controls the IoT equipment in real time with edge routers, have attracted attention as crucial techniques in the field of information, communication, and industries. In order to establish such technologies, it is essential not only to develop the technologies of upper layers such as application and architecture, but also to further improve the communication capacity of the core/metro optical communication network, optical/wireless communication in access network, and the network in data centers.The traffic growth of data centers and access networks including wireless links is especially higher than in other networks [1] because the connection from the Internet to individual users is mostly based on wireless communications. Therefore, more convenient communication and connectivity are expected in the next generation communication services such as beyond 5G mobiles. In order to realize such a large capacity data center and access network, novel photonic integrated circuits (PICs), which enable ultra-fast and large capacity communication, are indispensable, [2][3][4][5][6][7][8][9][10][11][12][13] besides improving communication capacity owing to newly developed modulation and system technologies. [14][15][16][17][18] In addition, characteristics such as low cost and energy consumption, and thermal stability at high temperatures are essential if the PICs are to be integrated with other electronic devices such as large-scale integrated circuits (LSIs). The temperature stability is especially important because heat diffused from LSIs causes a high surrounding temperature, which is detrimental to the operating conditions of PICs.In contrast, quantum dot (QD) is an extremely promising material or structure for high-performance optical devices owing to its delta function-like density of states. [19] Several groups have reported that laser diodes (LDs), [20][21][22][23] semiconductor optical amplifiers (SOAs), [24][25][26] and photodiodes (PDs) [27] that utilize...