Summary of significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Schedule of Product Information

Customers accounting for more than 10% of our total revenue and revenue from our top five customers for the years ended December 31, 2019, 2018 and 2017 were as follows: 

	Years Ended December 31,
	2019		2018		2017
Percent of revenue from customers accounting for 10% or more of total revenue:
Huawei Technologies Co., Ltd	41	%	46	%	40	%
Ciena Corporation	29	%	24	%	16	%
Percent of revenue from top five customers	84	%	87	%	78	%

Estimated Useful Lives of Property, Plant and Equipment

Depreciation and amortization are computed using the straight-line method over the following estimated useful lives: 

Buildings	20-30 years
Machinery and equipment	2-7 years
Furniture, fixtures and office equipment	3-5 years
Software	5-7 years
Leasehold improvements	life of the asset or lease term, if shorter