1 Introduction

1.1 Six Sigma, Telecommunications and Productivity

From the beginning of the quality movement, continuous improvement and innovation are essential elements to improve processes and performance metrics to achieve the competitiveness in modern organizations. These are the keystones of different models of performance excellence. Due to this the organizations, adopt different initiatives to reduce costs, increase productivity in their production lines, by forming quality circles or getting involved in continuous improvement projects (CIPs) [1]. Besides, Service excellence is not a slogan; It is a commitment to meet the changing needs and wants of customers [2].

(CIPs) involve a planned, organized, and systematic approach to improve organizational performance [3]. It is made up of teams with different backgrounds or from different departments and, with a focus on processes, work to improve the performance metrics of the organization’s processes and systems [4, 5]. There are various CIPs, and their application has been increasing in the last 20 years, making it possible to use various Lean methodology or tools such as 5S, Value stream Map (VSM) among others. Furthermore, it's implementation and maintenance, as in the case of Six Sigma or Lean Six Sigma takes time and financial resources [1] but, sometimes, organizations show difficulties in achieving the desired level of improvement or maintaining the results of the program [6].

Lean, as an excellence methodology of continuous improvement seeks to systematically eliminate waste in manufacturing processes [7]. For its part, Six Sigma seeks, through the DMAIC methodology (Define, Measure, Analyze, Improve and Control) complemented with statistical tools, improves the quality of the results of the process, identifying and eliminating the cause of defects and reducing the variability in the manufacturing processes [8, 9].

Sigma, as a statistical measure, shows the variation of a sampling distribution. However, in a business process, it implies reduction of product failures to a rate of 3.4 failures per million where the probability of producing faulty products is extremely small, having in this way a product of excellent quality [10].

The premise of Six Sigma is the definition of a specific measurable quantitative objective called, the “big Y”. To that extent, Six Sigma encourages experimentation and analysis of independent “X” variables by providing a roadmap of five phases designed to identify the root cause of a problem (DMAIC) [11].

Six Sigma is used in different manufacturing industries and service sectors [12], although it was originally designed for manufacturing and productivity improvements in the production process [13]. Furthermore, with its implementation in the service sector, it has demonstrated its contribution to improve the time of delivery, reduction of cycle time, increase in customer satisfaction, reduction in the cost of service and get a higher quality [14]. In its implementation, people are organized into different hierarchical levels identified by colored bands (belts), as in martial arts. As darker the band, more advanced the level and degree of maturity of the person in charge to lead the quality management process [10].

In general, Lean, SS and LSS methodologies are motivated to improve the multifunctional skills of the staff and management [15], improve the work environment [16], manage the adoption of new technological solutions [17], design a new process [18, 19], implement risk management effectively [20] and, focus organizational effort on patient value in hospital healthcare [21,22,23,24].

When solving Six Sigma problems, the DMAIC takes as reference the Deming cycle; while the DMADV (Define, Measure, Analyze, Design and Verify) consists of 5 interconnected stages and is a quality procedure based in information to plan elements and procedures allowing the creation of new structures for the design of a new product. By combining these two approaches, the efficiency, effectiveness, and productivity of the organization can be increased by accelerating the processes to achieve high performance [25].

The stages to implement a CIP Six sigma which involves the DMAIC include the following:

  • Define: The problem is identified and roles and objectives are assigned. It presents the current situation of the process and the points to improve, related to the critical characteristics of quality. The Pareto diagram and control charts are the most common quality tools used [26].

  • Measure: Allows to determine the flow and execution of the process. With this information, the efficiency is evaluated at each stage of this. Companies can use efficiency scores as indicators to quantify their performance. These indicators contribute to improving the sustainability performance and planning the necessary corrective actions [27].

  • Analyze: At this stage, having been defined the probable causes and the most significant variables that generate the variability, the capacity of the process to produce according to the proposed objectives must be evaluated [28].

  • Improve: Allows you to confirm the variables, seeking to optimize the process or reduce variability [29].

  • Control: Its purpose is to ensure that any gains obtained are preserved, until new knowledge and data demonstrate that there is a better way to operate the process [30].

The DMAIC approach allows identifying: problems, critical areas, anomalies and errors, propose solutions to prevent or minimize the causes of the problem, controlling and evaluating the results of the implemented solutions [11]. Other process improvement tools, such as total quality management (TQM), seek to build an organizational culture where all resources are used effectively and efficiently to face the competition and achieve its competitiveness objective in the long term [31] and the Internal quality control (IQC) is a set of procedures for a continuous supervision of operations having as a main objective to ensure the daily consistency of processes by detecting errors that may arise [32].

Finally, the implementation of DMAIC in the achievement of organizational objectives in the improvement of productivity contributes to avoid waste, producing goods without reducing product quality, reducing cost, produce small quantities quickly and delivering products without defects to the clients. It comprises three key elements: labor, equipment and raw materials and involves: the analysis of work processes, improvement of bottlenecks, elimination of waste among others, and plays a fundamental role in reducing operating costs and the increase of their profits [33].

2 Methodology

Case study is a research strategy focused on understanding the dynamics present in unique environments [34]. Individual case studies have been accepted as a valid research approach [35]. For the investigation, the researchers were required to manage and closely followed the deployment of the DMAIC methodology and the improvement project. Their participation in the leadership and support for the implementation and management are essential [36]. Thus, the proposal is similar to action research as a method to investigate and generate practical solutions with the participation of representatives of the case study companies in the research process [37]. The action research approach ensures to overcome the challenges presented in the application of Six-Sigma with the help of researchers. A team of three people was formed, a facilitator who acted as project manager providing Six-Sigma experience and two technicians in charge of operational activities [34].

3 Research Problem

3.1 Contextualization of Problematic Reality

Fiber optic networks have contributed to the improvement of quality of broadband services with high-speed data transmission over long distances. Among these, we have multimedia services with ultra-high-definition videos. It is achieved through optical communication techniques such as radio over fiber (RoF), fiber to the home (FTTH) and others [38]. The need for higher bandwidth connections has been driven by developments such as fifth generation (5G) wireless networks. The European Commission is working to achieve specific alternatives in relation to the development of next generation networks. Many EU countries have opted for a gradual migration path towards Fiber to the Home (FTTH) technology in view of the high costs of 5G technology [39]; However, despite these technological advances, the companies in charge of installing these services seek to improve their Operations and Maintenance (O&M) management methods, focusing on innovation and process simplification [40].

The organization is an outsourcing dedicated to make FTTH (Fiber To The Home) installations, also called “fiber to the premises” (FTTP), which is the installation of fiber optics from a central point directly to individual buildings such as residences, apartment buildings and companies. In this way, it is offered high-speed internet connection to users compared to other technologies [41]. Its main offices are in Lima, Peru and offers its services to telecommunications Carrier companies. Its main client is CLARO Perú, a subsidiary of AMÉRICA MOVIL, one of the leading companies that provides integrated telecommunications services with a presence in Central and South America, as well as Austria & Eastern Europe [42].

The scope of the investigation was concentrated in the operations area. This represents almost 60% of the payroll of the organization. The company’s records and historical data indicated that the area’s productivity for the first quarter of 2022 was below 50%. This problem affected the other divisions of the company, generating complaints from its client. This led to identify the root causes of the problem. From its analysis, it was proposed to undertake a CIP. Six Sigma was the tool selected.

Regarding the general research problem, this was defined as: How will the Six Sigma implementation increase productivity in the FTTH installation services process, in the organization’s operations area? The general objective proposed was Increase productivity in the FTTH installation services process in the organization’s operations area. The population and sample consisted of the FTTH installation services served by the company. For the execution of the service, 10 operations, 02 inspections and 02 combined operations were identified.

Operational activities begin when the technicians arrive at client’s home and activate the field service management software. It is managed from the cloud and keeps track of the time of the work to be carried out. Once the data about the address where the installation will take place has been verified, they arrange to start the work, taking safety measures and using the personal protective equipment (PPE). Using a telescopic ladder, the fiber optic is connected to the Fiber Access Terminal (FAT) installed at client’s home. In addition, the connection cable and internal wiring are carried out for the connection of the equipment. Once the equipment is configured and the service is activated, connectivity tests are carried out and photographic evidence is recorded and sent through a mobile application (APP). Finally, information is provided to the client about the service installed, preparing the conformity report with information about the installation and conformity of the service. When the activity is closed in the field service management software application managed from the cloud, the service is terminated (Tables 1, 2, 3 and Fig. 1).

Table 1. Pre-test DPO value, yield performance (%) and six sigma level
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Table 2. First DPO, DPMO values and six sigma level
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Table 3. Pretest productivity index
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Fig. 1.
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Graphic of Pretest productivity

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The implementation was approved by the general manager, who appointed a quality improvement team to implement it. The phases developed were:

Define Stage

The problem and objective were reviewed and an implementation plan was developed. Using the SIPOC diagram (Suppliers, Inputs, Process, Outputs, Customers).

It was detailed the FTTH installation process. In addition, action plans were prepared using worksheets for the DMAIC project table, project planning, the requirements established in the service and results, the SIPOC diagram and the checklist to be used in the different stages.

Measure Stage

It is key in implementation. Data was collected to be analyzed and get an idea about if the process met the user’s needs; so, the FTTH installation process was observed. The tools used in this stage made possible to select the data to measure and calculate the initial sigma level. Some of them were the measurement planning worksheet, the CTQ tree to identify the most critical output of the SIPOC, the data stratification factors that identify the most influential factors in the process, the calculation worksheet from Sigma, the forms to calculate DPMO – Yield the Define stage checklist.

To determine the initial Sigma level of the process, the conversion table was used to determine the level. For the initial measurements, the conversion table was used to determine the level.

Analyze Stage

Both data analysis was carried out, where the root cause of the defects was investigated, and process analysis examined down time and others that did not add value to the process. The tools for this analysis were: Pareto charts and trend charts for exploration, brainstorming and the cause-effect diagram for the identification of causes, relationship, and dispersion diagrams. The tools for process analysis included: the flow chart, the interfunctional process map, worksheets, maps and documentation of the processes as well as the checklist for this stage.

Improve Stage

Improvement options were analyzed considering solutions aimed at eliminating the causes and choosing the best option considering that the solution proposed is not expensive and it is approved by the general manager. The tools used help select solutions. Among them, the application of the rule-breaking technique that allows identifying phrases that contain assumptions was considered. Regarding the synthesis of the solutions, the affinity diagram and the practicality scale tool were applied. To select the solutions, the criteria matrix tool was used to select potential solutions. About the criteria considered for the application of the matrix were cost, time, impact on other areas, reduction of defects and complexity of the methodology. For large-scale implementation, the Gantt Chart was used to determine the times for the execution of the improvements. Likewise, training, required documentation, shared responsibility and measurement as such were also considered. To this extent, the training carried out achieved a participation of 95% of those involved. As part of the development of the solutions, it was proposed to develop a salary incentive policy and to develop a training plan for better control in execution. A manual of field supervision procedures, internal procedures for the support desk and internal procedures for technicians and their responsibilities were prepared.

Control Stage

The aim was to keep the process stable, because, without control, improved processes run the risk to return to the beginning, since it is very difficult to change old habits. With the improvements implemented, the performance of the process must be measured continuously using control and trend charts to detect any abnormal variation. The discipline obtained by the commitment to monitor and measure control tasks continuously played a very important role in this aspect. The documentation was evidenced by manuals that helped the responsible for the improved process to maintain it as such.

4 Results

4.1 Independent and Dependent Variable Results

After the implementation of Six Sigma, the data was taken considering the indicators already proposed. The results obtained were (Tables 4, 5, 6 and Fig. 2):

Table 4. Yield performance indicator with six sigma level on second evaluation
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Table 5. Details of second DPMO evaluation with six sigma level
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Table 6. Posttest productivity index
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Fig. 2.
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Graphic of posttest productivity

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5 Discussions

The purpose of the research was to increase productivity in the FTTH installation services process through the DMAIC methodology. In recent years, many companies have adopted this methodology to improve the quality of their products and reduce the amount of waste generated during the production process. The initial diagnosis was evidenced by the Ishikawa and Pareto diagrams. They allowed to identify 80% of the root causes of low productivity. For the case study, the company’s database was used, taking as reference the analysis of each of the causes. The improvement plan in the FTTH installation process increased productivity by 27.08% and even though the initial planned capacity was 21 services, because of the improvement this increased to 44 services.

According to [43], Six Sigma reduces errors, increases market share, optimizes cycle time, increases customer satisfaction, and improves productivity. Whereas for [44] quality improvement as an indicator of increasing process capacity contributes to increase productivity leading to competitiveness and contributing to the sustainability of the company. Furthermore, for [45] DMAIC method improve the process quality level of transistor spacers. On the other hand, [46] used the methodology to improve the production capacity and reduce the unit cost in the manufacturing of air conditioning equipment. Besides, [47] used the DMAIC cycle to improve processes and reduce the rejection percentage in brushless DC motors.

The results of descriptive analysis determined that the implementation of Six Sigma methodology in the FTTH installation process managed to increase productivity by 27.08%, efficiency by 14.52% and effectiveness by 11.69%. While according to [48] the DMAIC method decreased waste by 2.23%, environmental impact by 2.2% and increased global productivity by 2.4%. For his part [49] reduced the excessive cuts of meat, improving the process with increase of the income and reduction of waste.

Regarding the independent variable, it was possible to increase the performance level by 20%, the Sigma level by 26%, and the DPMO decreased by 40%. The work of [44] specified that the Sigma level control in a brushless motor manufacturing company increased between January to May 2022 by 5.44 compared to similar periods for the years 2020 and 2021, which were 4.93 and 5.11 respectively. Due to the improvement of the Sigma Level in the manufacturing company, it is demonstrated that Six Sigma is a good method that allows overcoming the problem of customer complaints.

Kaizen, as part of continuous improvement tools and practices for achieving operational excellence, eliminates activities that do not generate value due to incremental improvements [50] applied in a specific area in a relatively short period of time [51] where low-cost solutions and creativity are appealed [52]. Since the case study is associated with routine activities in the installation process of FTTH (Fiber To The Home) services and since the workers carry out their activities taking their field experience as a practice. It would be achieved better results in the application of six sigma with a greater standardization in operational work tasks derived from the use of procedures that are constantly reviewed and updated.

6 Conclusions

In relation to the general objective, it was concluded that productivity increased from 48% to 61%, with a percentage variation of 27.08%. Regarding effectiveness, this increased from 77% to 86%, with a percentage increase of 11.69% and efficiency increased from 62% to 71%, representing a percentage increase of 14.52% reflected in the reduction of unproductive times of human resources. Improvement actions must be applied continuously. This was reflected in the efficiency of the FTTH installation services process. It can be concluded that the objective of increase of productivity was met.

The research has limitations that restrict its generalization. As it is a case study and the results presented are based on a single organization, it is a limited sample to infer a generalization in the applicability of Six Sigma for the improvement of productivity to all companies that provide services of fiber optic installations (FTTH). Therefore, we consider it not advisable to generalize these results from a single case. On the other hand, since the data was collected during 30 days for the pretest and 30 days after the implementation of the improvement, this interval of time could be considered quite short; However, it provided valuable information that made it possible to carry out the study. Finally, even though productivity was the problem to solve; It is still true that it is also subject to other variables and conditions both inside and outside the organization.