Bit Error Ratio (BER) dependence on received power was studied for 40Gb/s NRZ short optical fiber transmission, including a series of four low return loss (RL~21dB) and low insertion loss (IL~0.1dB) connections. The calculated power penalty (PP) was 0.15dB for BER~10-11. Although the fiber length was within DFB laser’s coherent length of ~100m and the multi path interference (MPI) value was 34.3dB, no PP of BER was observed. There was no PP due to low MPI probably because the polarization of the signal pulses were not aligned for optical interference, indicating that NRZ systems have a high resistance to MPI.
The objective of this research was to investigate the impact of scratches on 40G NRZ optical link transmission and to understand if industry standards on connector scratches are sufficient for 40G applications.
A sample set of twelve optical cable assemblies were prepared and characterized by TE Connectivity. Each assembly was a mated connector pair. The samples were divided into six groups with different levels of polishing scratches applied to vary the Return Loss (RL) at the mating interface. The measured RL across all groups ranged from a minimum of 26 dB to a maximum greater than 80 dB. Experimental links were built based on a 40G NRZ Bit Error rate Tester, EDFA with attenuator, cable assemblies and a fiber (maximum up to 3 km ITU-T G.652.D fiber). Bit Error Rate (BER) curve, Eye diagram, Jitter and Q-factor were measured for all experimental links. We found there was no significant change in any of the measured parameters for the links with different connector assemblies but with the same fiber length of optical link. The 40G NRZ link with multiple cable assemblies (up to 4 samples) and a fiber (1 to 3km) demonstrated significant robustness to the connector scratches.
This paper summarizes the correlation study between contamination and scratches on singlemode APC connectors and
signal degradation; leading to an Acceptance Criteria Matrix. The study is a continuation of International Electronics
Manufacturing Initiative (iNEMI) research on development of cleanliness specification for singlemode angled physical
contact (SM-APC) connectors.
Twenty-five APC SC connectors on one-meter patch cords were used for this study. The Design of the Experiment
(DoE) was a multi-step process that involved: (1) inspecting, cleaning and inspecting connectors being tested (devices
under test, or DUTs) and launch connectors; (2) making multiple matings and dematings of each DUT, in a pristine state,
with a reference connector, and recording Return Loss (RL) data after each cycle; (3) manually applying dust to the
cleaned end-faces of the DUTs; then (4) mating contaminated DUTs with clean reference connectors at least five times,
taking RL measurements after each mating and saving fiber end-face images for both connectors. It was shown that
connectors with the contamination at the core (9um diameter) demonstrated a dramatic decrease in average RL of 14.2
dB. In comparison, the samples with contamination on the cladding and clear core demonstrated a negligible change in
RL of 0.15 dB. For highly contaminated samples in the cladding layer, we found the changes of RL to be about 5-6 dB.
Further investigation established that particle migration during successive matings also occurs on the ferrule within the
contact zone (approximately <250 μm in diameter). Polishing scratches had no impact on RL of APC connectors.
Based on the experimental data described in this paper, an inspection criteria matrix is proposed for SM-APC connectors
including the zone definitions and number of allowable defects (contamination and scratches) for each zone. The
recommendations on pass/fail criteria have been provided to the IEC (International Electrotechnical Committee). It is
expected IEC-61300-3-25, which contains these criteria, will publish in 2009.
The paper summarizes the research of the iNEMI (International Manufacturing Initiatives) project on Fiber Connector Endface Specifications focused on the development of the cleanliness specification of the receptacle modules. It will discuss (1) the critical parameters of Small Form-Factor (SFF&SFP) modules sensitive to the contamination, (2) the experimental contamination techniques, (3) the test and measurement methodology, as well as (4) the Gage R & R (Repeatability & Reproducibility) studies. We choose one of the standard OC-48, SFF modules manufactured by Sumitomo Electric as the experimental vehicle for the project. The influence of the SiO2 based dust with the particle size under 149 um on optical performance of SFF module has been investigated. The Optical Return Loss (ORL) has been identified as the most sensitive parameter to the contamination for the both transmitter and receiver optical endface. In a case of changes of the transmitter ORL by 20-25 dB due to the application of the contamination, the optical power and spectral width didn't change, and the pulse mask was reduced only by 2%. The contamination near the core area caused changes of the ORL by 20-30dB, and high standard deviation of ORL (0.5-2.1 dB). The Gage R & R study was focused on investigation of equipment repeatability, mating repeatability, and operator dependence for ORL measurement of clean and contaminated optical endface. The proposed experimental methodology was able to achieve all Gage R & R parameters within the required limits.
The contamination of fiber optics connectors has recently been recognized as an industry wide problem. The contamination has resulted in degradation of optical signal performance, which creates false fails during the manufacturing process. These contaminated fiber optics connectors require additional manufacturing operations such as inspection of incoming components, cleaning
process and re-inspection. The cleanliness of test connectors is also very important to ensure good product quality. The dirty connectors in the test environment create false functional failures at the
board level, resulting in unnecessary and costly rework. All precautions have to be taken to identify the critical steps in the manufacturing process that cause the contamination to the component,
assembly or board levels. The potential sources of contamination and the mechanisms of the transferring contamination have been analyzed.